Nix / NixOS

I'm quite new to NixOS and am currently running it inside a VM. I've been using Arch as my daily-driver for almost a year now.

How do i write a NixOS derivation to configure Doom Emacs for me?

I already have my init, config and packages.el files in my dotfiles private repo on Gitlab. Assuming I've already cloned these repos to my home directory, is it possible to create a Nix derivation for this purpose??

EDIT: I've setup my custom Emacs build, and the rest of the script automatically configures doom for me.