Ahah sure, feel free to do so ^^
Thanks for making the great NixOS & Flakes Book, @mars-monkey. You have done a wonderful job. I have been reading it today. However, I also got confused at the same spot as @RudiOnTheAir. As I followed the guide, I ended up trying to do a new build, using a configuration.nix that lacked key information (like boot.loader info). I had to add the line nix.settings.experimental-features = [ "nix-command" "flakes" ];, without removing the other info. I ended up having to look at the NixOS Wiki, to get past that point.
Sorry for the confusion; I didn’t write the NixOS and Flakes Book. I’ve used it to help me learn recently, but I’m nowhere near the level of experience to write something like that. That said, I recommend it to most early beginners as a pretty good place to start.
I’m not sure I completely understand your issue, but maybe if you make another post with some more details and tag me I’ll be able to help.