Installing Doom Emacs on NixOS

Versions of this question have been asked before, but I haven’t seen a definitive answer (that I’m capable of adapting). I’ve recently switched to NixOS, and can’t seem to install Doom the Nix way. I’ve had to install imperatively, like in the manual.

My NixOS config is basically identical to that in here. I already have my Doom config in a repo on Github, and I’m not trying to manage the modules/packages themselves through nix, just get NixOS to install doom and apply my config. How do I create a new package/overlay to do this? Does anyone have some experience here? I’d rather not use the nix-doom-emacs project as it’s pretty behind.