First off, I read and relate very much to Alternative to .config/nixpkgs/config.nix:packageOverrides - #3 by limeytexan.
I stumbled on this when following the install instructions here (to the user profile): GitHub - guibou/nixGL: A wrapper tool for nix OpenGL application.
Now my question is to how to make this and similar packages ready for flox. I am eyeballing Build and develop custom packages | flox:docs, but wanted to get some insight from the community for the specific nixGL package as well as ideas on these situations in general.