I'm using NixOS again after installing it years ago and enjoying it, but I still have a real hard time understanding just how to somehow implement or use a flake, or create a useful new package with it that isn't in the nixpkgs repo already.

I still find much of the syntax incredibly confusing and hard to just get simple concrete self contained examples, or without worrying if this is intermingled with some non flake code somewhere that isn't compatible.

I've bumped a few nix packages via github PR's and can hack around a bit with existing things I see upstream, but knowing how to do everything is still confusing.

I guess I need to sit down and read all of https://zero-to-nix.com/ and see if there is anything I'm missing.

What does this enable that will be useful to me as a user?