To build:
west build -b nrf5340dk_nrf5340_cpuapp
To flash:
west flash
If you get an error like:
FATAL ERROR: command exited with status 16: nrfjprog --program zephyr/zephyr.hex -f NRF53 --snr 960149330 --coprocessor CP_APPLICATION --sectorerase
you can "recoved" with the command:
nrfjprog --recover -f NRF53