I found this page very helpful in understanding each step of the QR code creation process. I can't say I recall it all but it would be possible to turn this into a small booklet, I guess.

https://typefully.com/DanHollick/qr-codes-T7tLlNi

Here's a HN discussion from 2022 about it.

https://news.ycombinator.com/item?id=32837565