neovim-flake/docs/manual/installation/custom-configuration.md

Standalone Installation

It is possible to install neovim-flake without depending on NixOS or home-manager as the parent module system, using the neovimConfiguration function exposed by neovim-flake extended library. It takes in the configuration as a module, and returns an attribute set as a result.

{
  options = "The options that were available to configure";
  config = "The outputted configuration";
  pkgs = "The package set used to evaluate the module";
  neovim = "The built neovim package";
}

standalone/nixos.md
standalone/home-manager.md