Root page cannot have children

[Vongsi]

Following the document below, seems it advised to set the page's template to blog/index. then there was an error

Any one faced the same error ?

https://statamic.dev/quick-start-guide#blog-index

Blog Index

Next, let's make that blog index page. Head back to the control panel and go to the Pages collection. Create a new entry and call it "Blog", "My Blog", or even "My CyberBlog" — just make sure the slug is blog. Set the template to blog/index.

[jelleroorda]

You can fix this by manually removing any children from the first entry in your tree in the content/trees/collections/pages.yaml file. If you have your collection set up to have a 'root' element, that element is not allowed to have any children.