A few month’s ago I merged a PR to Gutenberg Core for a new documentation tutorial called Building a custom block editor.
The tutorial was originally produced for my own learning, but I was encouraged to add it to the official documentation by members of the Gutenberg core team and the WordPress community.
The tutorial comes with an accompanying repository so you can check out the code yourself. I’m trying to keep it updated when I can!
Did you find the tutorial useful? If so please do let me know in the comments below.