When I was learning Nix a few months back, I found the community often suggesting flakes as an improvements to some of the rough edges that were encountered, yet the flakes documentation is fragemented and largely targeted at audiences that already know basic Nix, so is detailed as differences from the current model.
So I wrote a guide that starts from the basics with the new CLI and builds up to flakes, you can see it here:
https://tonyfinn.com/blog/nix-from-first-principles-flake-edition/
Thereās 8 parts so far and it now covers enough I feel comfortable sharing it, as it now covers the basics of Nix and flakes, but I do plan to add more in the future to cover things like NixOS, overlays, home-manager etc. (Also maybe NixOps, but I need to learn NixOps myself first).