diff --git a/pkg/build/accounts.go b/pkg/build/accounts.go
index 7d47d9504..2abc8e568 100644
--- a/pkg/build/accounts.go
+++ b/pkg/build/accounts.go
@@ -27,9 +27,7 @@ import (
 	"chainguard.dev/apko/pkg/passwd"
 )
 
-func (di *buildImplementation) appendGroup(
-	o *options.Options, groups []passwd.GroupEntry, group types.Group,
-) []passwd.GroupEntry {
+func appendGroup(o *options.Options, groups []passwd.GroupEntry, group types.Group) []passwd.GroupEntry {
 	o.Logger().Printf("creating group %d(%s)", group.GID, group.GroupName)
 
 	ge := passwd.GroupEntry{
@@ -57,9 +55,7 @@ func userToUserEntry(user types.User) passwd.UserEntry {
 	}
 }
 
-func (di *buildImplementation) MutateAccounts(
-	fsys apkfs.FullFS, o *options.Options, ic *types.ImageConfiguration,
-) error {
+func mutateAccounts(fsys apkfs.FullFS, o *options.Options, ic *types.ImageConfiguration) error {
 	var eg errgroup.Group
 
 	if len(ic.Accounts.Groups) != 0 {
@@ -73,7 +69,7 @@ func (di *buildImplementation) MutateAccounts(
 			}
 
 			for _, g := range ic.Accounts.Groups {
-				gf.Entries = di.appendGroup(o, gf.Entries, g)
+				gf.Entries = appendGroup(o, gf.Entries, g)
 			}
 
 			if err := gf.WriteFile(fsys, path); err != nil {
diff --git a/pkg/build/build.go b/pkg/build/build.go
index ea4bfcc64..c27023ee5 100644
--- a/pkg/build/build.go
+++ b/pkg/build/build.go
@@ -21,23 +21,17 @@ import (
 	"context"
 	"encoding/hex"
 	"fmt"
-	"hash"
 	"io"
-	"io/fs"
 	"os"
 	"runtime"
 	"strconv"
 	"strings"
 	"time"
 
-	apkimpl "github.com/chainguard-dev/go-apk/pkg/apk"
 	apkfs "github.com/chainguard-dev/go-apk/pkg/fs"
-	"github.com/google/go-containerregistry/pkg/name"
 	v1 "github.com/google/go-containerregistry/pkg/v1"
 	v1types "github.com/google/go-containerregistry/pkg/v1/types"
 	"github.com/hashicorp/go-multierror"
-	coci "github.com/sigstore/cosign/v2/pkg/oci"
-	"gitlab.alpinelinux.org/alpine/go/repository"
 	"go.opentelemetry.io/otel"
 	"gopkg.in/yaml.v3"
 
@@ -53,7 +47,6 @@ import (
 // architecture emulation, the s6 supervisor to add to the image,
 // build options, and the `buildImplementation`, which handles the actual build.
 type Context struct {
-	impl *buildImplementation
 	// ImageConfiguration instructions to use for the build, normally from an apko.yaml file, but can be set directly.
 	ImageConfiguration types.ImageConfiguration
 	// ImageConfigFile path to the config file used, if any, to load the ImageConfiguration
@@ -70,37 +63,6 @@ func (bc *Context) Summarize() {
 	bc.ImageConfiguration.Summarize(bc.Logger())
 }
 
-// BuildTarball calls the underlying implementation's BuildTarball
-// which takes the fully populated working directory and saves it to
-// an OCI image layer tar.gz file.
-func (bc *Context) BuildTarball(ctx context.Context) (string, hash.Hash, hash.Hash, int64, error) {
-	return bc.impl.BuildTarball(ctx, &bc.Options, bc.fs)
-}
-
-// WriteIndex calls the underlying implementation's WriteIndex
-// which takes the an index struct and saves it to the working directory.
-func (bc *Context) WriteIndex(idx coci.SignedImageIndex) (string, int64, error) {
-	return bc.impl.WriteIndex(&bc.Options, idx)
-}
-
-func (bc *Context) GenerateImageSBOM(ctx context.Context, arch types.Architecture, img coci.SignedImage) ([]types.SBOM, error) {
-	opts := bc.Options
-	opts.Arch = arch
-	return bc.impl.GenerateImageSBOM(ctx, &opts, &bc.ImageConfiguration, img)
-}
-
-func (bc *Context) GenerateIndexSBOM(ctx context.Context, indexDigest name.Digest, imgs map[types.Architecture]coci.SignedImage) ([]types.SBOM, error) {
-	return bc.impl.GenerateIndexSBOM(ctx, &bc.Options, &bc.ImageConfiguration, indexDigest, imgs)
-}
-
-func (bc *Context) GenerateSBOM(ctx context.Context, digest v1.Hash) error {
-	return bc.impl.GenerateSBOM(ctx, &bc.Options, &bc.ImageConfiguration, digest)
-}
-
-func (bc *Context) InstalledPackages() ([]*apkimpl.InstalledPackage, error) {
-	return bc.impl.InstalledPackages(bc.fs, &bc.Options)
-}
-
 func (bc *Context) GetBuildDateEpoch() (time.Time, error) {
 	if _, ok := os.LookupEnv("SOURCE_DATE_EPOCH"); ok {
 		return bc.Options.SourceDateEpoch, nil
@@ -118,9 +80,8 @@ func (bc *Context) GetBuildDateEpoch() (time.Time, error) {
 	return bde, nil
 }
 
-func (bc *Context) BuildImage(ctx context.Context) (fs.FS, error) {
-	// TODO(puerco): Point to final interface (see comment on buildImage fn)
-	if err := buildImage(ctx, bc.fs, bc.impl, &bc.Options, &bc.ImageConfiguration, bc.s6); err != nil {
+func (bc *Context) BuildImage(ctx context.Context) error {
+	if err := bc.buildImage(ctx); err != nil {
 		logger := bc.Options.Logger()
 		logger.Debugf("buildImage failed: %v", err)
 		b, err2 := yaml.Marshal(bc.ImageConfiguration)
@@ -129,14 +90,9 @@ func (bc *Context) BuildImage(ctx context.Context) (fs.FS, error) {
 		} else {
 			logger.Debugf("image configuration:\n%s", string(b))
 		}
-		return nil, err
+		return err
 	}
-	return bc.fs, nil
-}
-
-func (bc *Context) BuildPackageList(ctx context.Context) (toInstall []*repository.RepositoryPackage, conflicts []string, err error) {
-	// TODO(puerco): Point to final interface (see comment on buildImage fn)
-	return buildPackageList(ctx, bc.fs, bc.impl, &bc.Options, &bc.ImageConfiguration)
+	return nil
 }
 
 func (bc *Context) Logger() log.Logger {
@@ -157,7 +113,7 @@ func (bc *Context) BuildLayer(ctx context.Context) (string, v1.Layer, error) {
 	bc.Summarize()
 
 	// build image filesystem
-	if _, err := bc.BuildImage(ctx); err != nil {
+	if err := bc.BuildImage(ctx); err != nil {
 		return "", nil, err
 	}
 
@@ -234,10 +190,7 @@ func New(workDir string, opts ...Option) (*Context, error) {
 	fs := apkfs.DirFS(workDir, apkfs.WithCreateDir())
 	bc := Context{
 		Options: options.Default,
-		impl: &buildImplementation{
-			workdirFS: fs,
-		},
-		fs: fs,
+		fs:      fs,
 	}
 	bc.Options.WorkDir = workDir
 
@@ -275,16 +228,11 @@ func New(workDir string, opts ...Option) (*Context, error) {
 	return &bc, nil
 }
 
-// Refresh initializes the build process by calling the underlying implementation's
-// Refresh(), which includes getting the chroot/proot jailed process executor (and
-// possibly architecture emulator), sets those on the Context, and returns.
+// Refresh initializes the build process by creating a new s6 context.
 func (bc *Context) Refresh() error {
-	s6, err := bc.impl.Refresh(&bc.Options)
-	if err != nil {
-		return err
-	}
+	bc.Options.TarballPath = ""
 
-	bc.s6 = s6
+	bc.s6 = s6.New(bc.fs, bc.Logger())
 
 	return nil
 }
diff --git a/pkg/build/build_implementation.go b/pkg/build/build_implementation.go
index f50797c21..327a9062e 100644
--- a/pkg/build/build_implementation.go
+++ b/pkg/build/build_implementation.go
@@ -22,10 +22,8 @@ import (
 	"fmt"
 	"hash"
 	"io"
-	"io/fs"
 	"os"
 	"path/filepath"
-	"runtime"
 
 	gzip "github.com/klauspost/pgzip"
 	"go.opentelemetry.io/otel"
@@ -36,40 +34,25 @@ import (
 	"github.com/google/go-containerregistry/pkg/name"
 	v1 "github.com/google/go-containerregistry/pkg/v1"
 	ggcrtypes "github.com/google/go-containerregistry/pkg/v1/types"
-	coci "github.com/sigstore/cosign/v2/pkg/oci"
+	"github.com/sigstore/cosign/v2/pkg/oci"
 	"gitlab.alpinelinux.org/alpine/go/repository"
 	khash "sigs.k8s.io/release-utils/hash"
 
 	chainguardAPK "chainguard.dev/apko/pkg/apk"
 	"chainguard.dev/apko/pkg/build/types"
 	"chainguard.dev/apko/pkg/options"
-	"chainguard.dev/apko/pkg/s6"
 	"chainguard.dev/apko/pkg/sbom"
 	soptions "chainguard.dev/apko/pkg/sbom/options"
 )
 
-const indexFile = "index.json"
-
-type buildImplementation struct {
-	workdirFS apkfs.FullFS
-}
-
-func (di *buildImplementation) Refresh(o *options.Options) (*s6.Context, error) {
-	o.TarballPath = ""
-
-	hostArch := types.ParseArchitecture(runtime.GOARCH)
-
-	if !o.Arch.Compatible(hostArch) {
-		o.Logger().Warnf("%q requires QEMU binfmt emulation to be configured (not compatible with %q)", o.Arch, hostArch)
-	}
-
-	return s6.New(di.workdirFS, o.Logger()), nil
-}
-
-func (di *buildImplementation) BuildTarball(ctx context.Context, o *options.Options, fsys fs.FS) (string, hash.Hash, hash.Hash, int64, error) {
+// BuildTarball takes the fully populated working directory and saves it to
+// an OCI image layer tar.gz file.
+func (bc *Context) BuildTarball(ctx context.Context) (string, hash.Hash, hash.Hash, int64, error) {
 	ctx, span := otel.Tracer("apko").Start(ctx, "BuildTarball")
 	defer span.End()
 
+	o := bc.Options
+
 	var outfile *os.File
 	var err error
 
@@ -99,7 +82,7 @@ func (di *buildImplementation) BuildTarball(ctx context.Context, o *options.Opti
 
 	diffid := sha256.New()
 
-	if err := tw.WriteTar(ctx, io.MultiWriter(diffid, gzw), fsys); err != nil {
+	if err := tw.WriteTar(ctx, io.MultiWriter(diffid, gzw), bc.fs); err != nil {
 		return "", nil, nil, 0, fmt.Errorf("failed to generate tarball for image: %w", err)
 	}
 	if err := gzw.Close(); err != nil {
@@ -119,8 +102,11 @@ func (di *buildImplementation) BuildTarball(ctx context.Context, o *options.Opti
 	return outfile.Name(), diffid, digest, stat.Size(), nil
 }
 
-// GenerateImageSBOM generates an sbom for an image
-func (di *buildImplementation) GenerateImageSBOM(ctx context.Context, o *options.Options, ic *types.ImageConfiguration, img coci.SignedImage) ([]types.SBOM, error) {
+func (bc *Context) GenerateImageSBOM(ctx context.Context, arch types.Architecture, img oci.SignedImage) ([]types.SBOM, error) {
+	ic := bc.ImageConfiguration
+	o := bc.Options
+	o.Arch = arch
+
 	ctx, span := otel.Tracer("apko").Start(ctx, "GenerateImageSBOM")
 	defer span.End()
 
@@ -129,7 +115,7 @@ func (di *buildImplementation) GenerateImageSBOM(ctx context.Context, o *options
 		return nil, nil
 	}
 
-	s := newSBOM(di.workdirFS, o, ic)
+	s := newSBOM(bc.fs, &o, &ic)
 
 	m, err := img.Manifest()
 	if err != nil {
@@ -178,16 +164,19 @@ func (di *buildImplementation) GenerateImageSBOM(ctx context.Context, o *options
 }
 
 // GenerateSBOM generates an SBOM for an apko layer
-func (di *buildImplementation) GenerateSBOM(ctx context.Context, o *options.Options, ic *types.ImageConfiguration, digest v1.Hash) error {
+func (bc *Context) GenerateSBOM(ctx context.Context, digest v1.Hash) error {
 	ctx, span := otel.Tracer("apko").Start(ctx, "GenerateSBOM")
 	defer span.End()
 
+	o := bc.Options
+	ic := bc.ImageConfiguration
+
 	if len(o.SBOMFormats) == 0 {
 		o.Logger().Warnf("skipping SBOM generation")
 		return nil
 	}
 
-	s := newSBOM(di.workdirFS, o, ic)
+	s := newSBOM(bc.fs, &o, &ic)
 
 	if err := s.SetLayerDigest(ctx, digest); err != nil {
 		return fmt.Errorf("reading layer tar: %w", err)
@@ -210,39 +199,15 @@ func (di *buildImplementation) GenerateSBOM(ctx context.Context, o *options.Opti
 	return nil
 }
 
-func (di *buildImplementation) InitializeApk(ctx context.Context, fsys apkfs.FullFS, o *options.Options, ic *types.ImageConfiguration) error {
-	apk, err := chainguardAPK.NewWithOptions(fsys, *o)
-	if err != nil {
-		return err
-	}
-	return apk.Initialize(ctx, ic)
-}
-
-func (di *buildImplementation) InstallPackages(ctx context.Context, fsys apkfs.FullFS, o *options.Options, ic *types.ImageConfiguration) error {
-	apk, err := chainguardAPK.NewWithOptions(fsys, *o)
-	if err != nil {
-		return err
-	}
-	return apk.Install(ctx)
-}
-
-func (di *buildImplementation) InstalledPackages(fsys apkfs.FullFS, o *options.Options) ([]*apkimpl.InstalledPackage, error) {
-	apk, err := chainguardAPK.NewWithOptions(fsys, *o)
+func (bc *Context) InstalledPackages() ([]*apkimpl.InstalledPackage, error) {
+	apk, err := chainguardAPK.NewWithOptions(bc.fs, bc.Options)
 	if err != nil {
 		return nil, err
 	}
 	return apk.GetInstalled()
 }
 
-func (di *buildImplementation) ResolvePackages(ctx context.Context, fsys apkfs.FullFS, o *options.Options, ic *types.ImageConfiguration) (toInstall []*repository.RepositoryPackage, conflicts []string, err error) {
-	apk, err := chainguardAPK.NewWithOptions(fsys, *o)
-	if err != nil {
-		return nil, nil, err
-	}
-	return apk.ResolvePackages(ctx)
-}
-
-func (di *buildImplementation) AdditionalTags(fsys apkfs.FullFS, o *options.Options) error {
+func additionalTags(fsys apkfs.FullFS, o *options.Options) error {
 	at, err := chainguardAPK.AdditionalTags(fsys, *o)
 	if err != nil {
 		return err
@@ -254,60 +219,45 @@ func (di *buildImplementation) AdditionalTags(fsys apkfs.FullFS, o *options.Opti
 	return nil
 }
 
-func (di *buildImplementation) BuildImage(
-	ctx context.Context,
-	o *options.Options, ic *types.ImageConfiguration, s6context *s6.Context,
-) (fs.FS, error) {
-	if err := buildImage(ctx, di.workdirFS, di, o, ic, s6context); err != nil {
-		return nil, err
-	}
-	return di.workdirFS, nil
-}
-
-// buildImage is a temporary function to make the fakes work.
-// This function only installs everything onto a temporary filesystem path
-// as defined by o.WorkDir.
-// A later stage should add things like busybox symlinks or ldconfig, etc.
-// after which it can be loaded into a tarball.
-//
-// TODO(puerco): In order to have a structure we can mock, we need to split
-// image building to its own interface or split out to its own package.
-func buildImage(
-	ctx context.Context,
-	fsys apkfs.FullFS, di *buildImplementation, o *options.Options, ic *types.ImageConfiguration,
-	s6context *s6.Context,
-) error {
+func (bc *Context) buildImage(ctx context.Context) error {
 	ctx, span := otel.Tracer("apko").Start(ctx, "buildImage")
 	defer span.End()
 
+	fsys, o, ic := bc.fs, &bc.Options, &bc.ImageConfiguration
+
 	o.Logger().Infof("doing pre-flight checks")
-	if err := di.ValidateImageConfiguration(ic); err != nil {
+	if err := ic.Validate(); err != nil {
 		return fmt.Errorf("failed to validate configuration: %w", err)
 	}
 
 	o.Logger().Infof("building image fileystem in %s", o.WorkDir)
 
-	if err := di.InitializeApk(ctx, fsys, o, ic); err != nil {
+	apk, err := chainguardAPK.NewWithOptions(fsys, *o)
+	if err != nil {
+		return err
+	}
+
+	if err := apk.Initialize(ctx, ic); err != nil {
 		return fmt.Errorf("initializing apk: %w", err)
 	}
 
-	if err := di.InstallPackages(ctx, fsys, o, ic); err != nil {
+	if err := apk.Install(ctx); err != nil {
 		return fmt.Errorf("installing apk packages: %w", err)
 	}
 
-	if err := di.AdditionalTags(fsys, o); err != nil {
+	if err := additionalTags(fsys, o); err != nil {
 		return fmt.Errorf("adding additional tags: %w", err)
 	}
 
-	if err := di.MutateAccounts(fsys, o, ic); err != nil {
+	if err := mutateAccounts(fsys, o, ic); err != nil {
 		return fmt.Errorf("failed to mutate accounts: %w", err)
 	}
 
-	if err := di.MutatePaths(fsys, o, ic); err != nil {
+	if err := mutatePaths(fsys, o, ic); err != nil {
 		return fmt.Errorf("failed to mutate paths: %w", err)
 	}
 
-	if err := di.GenerateOSRelease(fsys, o, ic); err != nil {
+	if err := GenerateOSRelease(fsys, o, ic); err != nil {
 		if errors.Is(err, ErrOSReleaseAlreadyPresent) {
 			o.Logger().Warnf("did not generate /etc/os-release: %v", err)
 		} else {
@@ -315,22 +265,22 @@ func buildImage(
 		}
 	}
 
-	if err := di.WriteSupervisionTree(s6context, ic); err != nil {
+	if err := bc.s6.WriteSupervisionTree(ic.Entrypoint.Services); err != nil {
 		return fmt.Errorf("failed to write supervision tree: %w", err)
 	}
 
 	// add busybox symlinks
-	if err := di.InstallBusyboxLinks(fsys, o); err != nil {
+	if err := installBusyboxLinks(fsys, o); err != nil {
 		return err
 	}
 
 	// add ldconfig links
-	if err := di.InstallLdconfigLinks(fsys); err != nil {
+	if err := installLdconfigLinks(fsys); err != nil {
 		return err
 	}
 
 	// add necessary character devices
-	if err := di.InstallCharDevices(fsys); err != nil {
+	if err := installCharDevices(fsys); err != nil {
 		return err
 	}
 
@@ -340,8 +290,10 @@ func buildImage(
 }
 
 // WriteIndex saves the index file from the given image configuration.
-func (di *buildImplementation) WriteIndex(o *options.Options, idx coci.SignedImageIndex) (string, int64, error) {
-	outfile := filepath.Join(o.TempDir(), indexFile)
+func (bc *Context) WriteIndex(idx oci.SignedImageIndex) (string, int64, error) {
+	o := bc.Options
+
+	outfile := filepath.Join(o.TempDir(), "index.json")
 
 	b, err := idx.RawManifest()
 	if err != nil {
@@ -360,22 +312,24 @@ func (di *buildImplementation) WriteIndex(o *options.Options, idx coci.SignedIma
 	return outfile, stat.Size(), nil
 }
 
-func buildPackageList(
-	ctx context.Context,
-	fsys apkfs.FullFS, di *buildImplementation, o *options.Options, ic *types.ImageConfiguration,
-) (toInstall []*repository.RepositoryPackage, conflicts []string, err error) {
+func (bc *Context) BuildPackageList(ctx context.Context) (toInstall []*repository.RepositoryPackage, conflicts []string, err error) {
+	fsys, o, ic := bc.fs, &bc.Options, &bc.ImageConfiguration
 	o.Logger().Infof("doing pre-flight checks")
-	if err := di.ValidateImageConfiguration(ic); err != nil {
+	if err := ic.Validate(); err != nil {
 		return toInstall, conflicts, fmt.Errorf("failed to validate configuration: %w", err)
 	}
 
 	o.Logger().Infof("building apk info in %s", o.WorkDir)
 
-	if err := di.InitializeApk(ctx, fsys, o, ic); err != nil {
+	apk, err := chainguardAPK.NewWithOptions(fsys, *o)
+	if err != nil {
+		return toInstall, conflicts, fmt.Errorf("initializing apk: %w", err)
+	}
+	if err := apk.Initialize(ctx, ic); err != nil {
 		return toInstall, conflicts, fmt.Errorf("initializing apk: %w", err)
 	}
 
-	if toInstall, conflicts, err = di.ResolvePackages(ctx, fsys, o, ic); err != nil {
+	if toInstall, conflicts, err = apk.ResolvePackages(ctx); err != nil {
 		return toInstall, conflicts, fmt.Errorf("resolving apk packages: %w", err)
 	}
 	o.Logger().Infof("finished gathering apk info in %s", o.WorkDir)
@@ -414,20 +368,19 @@ func newSBOM(fsys apkfs.FullFS, o *options.Options, ic *types.ImageConfiguration
 	return s
 }
 
-func (di *buildImplementation) GenerateIndexSBOM(
-	ctx context.Context,
-	o *options.Options, ic *types.ImageConfiguration,
-	indexDigest name.Digest, imgs map[types.Architecture]coci.SignedImage,
-) ([]types.SBOM, error) {
+func (bc *Context) GenerateIndexSBOM(ctx context.Context, indexDigest name.Digest, imgs map[types.Architecture]oci.SignedImage) ([]types.SBOM, error) {
 	_, span := otel.Tracer("apko").Start(ctx, "GenerateIndexSBOM")
 	defer span.End()
 
+	o := bc.Options
+	ic := bc.ImageConfiguration
+
 	if len(o.SBOMFormats) == 0 {
 		o.Logger().Warnf("skipping index SBOM generation")
 		return nil, nil
 	}
 
-	s := newSBOM(di.workdirFS, o, ic)
+	s := newSBOM(bc.fs, &o, &ic)
 	o.Logger().Infof("Generating index SBOM")
 
 	// Add the image digest
diff --git a/pkg/build/busybox.go b/pkg/build/busybox.go
index 5d7e86b8f..b03490929 100644
--- a/pkg/build/busybox.go
+++ b/pkg/build/busybox.go
@@ -53,7 +53,7 @@ var busyboxLinks map[string][]string
 // note that it changes based on version of busybox,
 // so this should be updated to match busybox version.
 
-func (di *buildImplementation) InstallBusyboxLinks(fsys apkfs.FullFS, o *options.Options) error {
+func installBusyboxLinks(fsys apkfs.FullFS, o *options.Options) error {
 	// does busybox exist? if not, do not bother with symlinks
 	if _, err := fsys.Stat(busybox); err != nil {
 		if !errors.Is(err, os.ErrNotExist) {
diff --git a/pkg/build/busybox_test.go b/pkg/build/busybox_test.go
index 57c95efec..dfa5dfd89 100644
--- a/pkg/build/busybox_test.go
+++ b/pkg/build/busybox_test.go
@@ -50,12 +50,11 @@ func TestInstallBusyboxSymlinks(t *testing.T) {
 	}
 	t.Run("with busybox-paths manifest", func(t *testing.T) {
 		var err error
-		di := &buildImplementation{}
 		fsys := apkfs.NewMemFS()
 		buildBusybox(fsys, t)
 		err = fsys.WriteFile("/etc/busybox-paths.d/busybox", []byte(strings.Join(fakeLinks, "\n")), 0755)
 		require.NoError(t, err)
-		err = di.InstallBusyboxLinks(fsys, &options.Options{})
+		err = installBusyboxLinks(fsys, &options.Options{})
 		require.NoError(t, err)
 		for _, link := range fakeLinks {
 			_, err := fsys.Lstat(link)
@@ -71,10 +70,9 @@ func TestInstallBusyboxSymlinks(t *testing.T) {
 	})
 	t.Run("without busybox-paths manifest", func(t *testing.T) {
 		var err error
-		di := &buildImplementation{}
 		fsys := apkfs.NewMemFS()
 		buildBusybox(fsys, t)
-		err = di.InstallBusyboxLinks(fsys, &options.Options{})
+		err = installBusyboxLinks(fsys, &options.Options{})
 		require.NoError(t, err)
 		for _, link := range fakeLinks {
 			_, err := fsys.Lstat(link)
diff --git a/pkg/build/chardevices.go b/pkg/build/chardevices.go
index 4f159b6e1..87e709ce4 100644
--- a/pkg/build/chardevices.go
+++ b/pkg/build/chardevices.go
@@ -8,7 +8,7 @@ import (
 	"golang.org/x/sys/unix"
 )
 
-func (di *buildImplementation) InstallCharDevices(fsys apkfs.FullFS) error {
+func installCharDevices(fsys apkfs.FullFS) error {
 	devices := []struct {
 		path  string
 		major uint32
diff --git a/pkg/build/image_builder.go b/pkg/build/image_builder.go
deleted file mode 100644
index f85612912..000000000
--- a/pkg/build/image_builder.go
+++ /dev/null
@@ -1,43 +0,0 @@
-// Copyright 2022, 2023 Chainguard, Inc.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-package build
-
-import (
-	"fmt"
-
-	"chainguard.dev/apko/pkg/build/types"
-	"chainguard.dev/apko/pkg/s6"
-)
-
-func (di *buildImplementation) ValidateImageConfiguration(ic *types.ImageConfiguration) error {
-	if err := ic.Validate(); err != nil {
-		return fmt.Errorf("failed to validate configuration: %w", err)
-	}
-	return nil
-}
-
-func (di *buildImplementation) WriteSupervisionTree(
-	s6context *s6.Context, imageConfig *types.ImageConfiguration,
-) error {
-	// write service supervision tree
-	s6m := make(map[interface{}]interface{}, len(imageConfig.Entrypoint.Services))
-	for k, v := range imageConfig.Entrypoint.Services {
-		s6m[k] = v
-	}
-	if err := s6context.WriteSupervisionTree(s6m); err != nil {
-		return fmt.Errorf("failed to write supervision tree: %w", err)
-	}
-	return nil
-}
diff --git a/pkg/build/ldconfig.go b/pkg/build/ldconfig.go
index 0d174055e..1a67929c8 100644
--- a/pkg/build/ldconfig.go
+++ b/pkg/build/ldconfig.go
@@ -101,7 +101,7 @@ func getSoname(vfs apkfs.OpenReaderAtFS, path string) (string, error) {
 	return dynStrings[0], nil
 }
 
-func (di *buildImplementation) InstallLdconfigLinks(fsys apkfs.FullFS) error {
+func installLdconfigLinks(fsys apkfs.FullFS) error {
 	linksMap, err := ldconfig(fsys, "/lib")
 	if err != nil {
 		return err
diff --git a/pkg/build/os-release.go b/pkg/build/os-release.go
index 3f76ddfd9..b33fb862c 100644
--- a/pkg/build/os-release.go
+++ b/pkg/build/os-release.go
@@ -26,9 +26,7 @@ import (
 	"chainguard.dev/apko/pkg/options"
 )
 
-func maybeGenerateVendorReleaseFile(
-	fsys apkfs.FullFS, ic *types.ImageConfiguration,
-) error {
+func maybeGenerateVendorReleaseFile(fsys apkfs.FullFS, ic *types.ImageConfiguration) error {
 	if ic.OSRelease.ID == "" || ic.OSRelease.VersionID == "" {
 		return nil
 	}
@@ -54,9 +52,7 @@ func maybeGenerateVendorReleaseFile(
 	return nil
 }
 
-func (di *buildImplementation) GenerateOSRelease(
-	fsys apkfs.FullFS, o *options.Options, ic *types.ImageConfiguration,
-) error {
+func GenerateOSRelease(fsys apkfs.FullFS, o *options.Options, ic *types.ImageConfiguration) error {
 	path := filepath.Join("etc", "os-release")
 
 	osReleaseExists := true
diff --git a/pkg/build/paths.go b/pkg/build/paths.go
index 8c243f7cf..cd2361a6c 100644
--- a/pkg/build/paths.go
+++ b/pkg/build/paths.go
@@ -138,9 +138,7 @@ func mutateSymLink(fsys apkfs.FullFS, o *options.Options, mut types.PathMutation
 	return nil
 }
 
-func (di *buildImplementation) MutatePaths(
-	fsys apkfs.FullFS, o *options.Options, ic *types.ImageConfiguration,
-) error {
+func mutatePaths(fsys apkfs.FullFS, o *options.Options, ic *types.ImageConfiguration) error {
 	for _, mut := range ic.Paths {
 		pm, ok := pathMutators[mut.Type]
 		if !ok {
diff --git a/pkg/s6/s6.go b/pkg/s6/s6.go
index b57b42c30..a6cd79839 100644
--- a/pkg/s6/s6.go
+++ b/pkg/s6/s6.go
@@ -20,7 +20,7 @@ import (
 	"chainguard.dev/apko/pkg/log"
 )
 
-type Services map[interface{}]interface{}
+type Services map[string]string
 
 type Context struct {
 	fs  apkfs.FullFS
diff --git a/pkg/s6/supervision_tree.go b/pkg/s6/supervision_tree.go
index 1d6eaf01c..37e018e29 100644
--- a/pkg/s6/supervision_tree.go
+++ b/pkg/s6/supervision_tree.go
@@ -15,7 +15,6 @@
 package s6
 
 import (
-	"errors"
 	"fmt"
 	"os"
 	"path/filepath"
@@ -64,18 +63,9 @@ func (sc *Context) WriteSupervisionTree(services Services) error {
 	sc.Log.Infof("generating supervision tree")
 
 	// generate the leaves
-	for service, descriptor := range services {
-		service, ok := service.(string)
-		if !ok {
-			return errors.New("service name is not string")
-		}
-
-		if svccmd, ok := descriptor.(string); ok {
-			if err := sc.WriteSupervisionServiceSimple(service, svccmd); err != nil {
-				return err
-			}
-		} else {
-			return errors.New("complex services are not yet supported")
+	for service, svccmd := range services {
+		if err := sc.WriteSupervisionServiceSimple(service, svccmd); err != nil {
+			return err
 		}
 	}