My NixOS configuration is modular by design. In practice, this means that you can build a NixOS configuration for your own machine by selecting any combination of these 3 variables:
$HOST -> this refers to the host-specific configuration (packages, services, etc). This loads the host-specific configuration from /hosts/$HOST/default.nix
$HARDWARE -> this refers to the hardware-specific configuration (disks, kernel, boot, etc). This loads the hardware-specific configuration from /hosts/$HARDWARE/default.nix
$ARCH -> this refers to the architecture of the configuration (x86_64-linux, aarch64-darwin, etc). This sets the architecture to use for the packages.
An example complete configuration could be: phobos-laptop-x86_64-linux [This is my personal laptop configuration :)]
All these variables are declared in the flake.nix and can be added/removed to fit your needs.
Make sure you're in the nixos-config folder and have followed (if necessary) the partitioning steps :)
$ nixos-install --flake .#$HOST-$HARDWARE-$ARCH
$ nix flake update
$ nixos-rebuild switch --flake .#$HOST-$HARDWARE-$ARCH
$ nix build .#homeManagerConfigurations.$HOST-$HARDWARE-$ARCH.activationPackage
$ ./result/activate
$ nix flake update
$ home-manager switch --flake .#$HOST-$HARDWARE-$ARCH
$ nix build .#isoConfigurations.$HOST-$HARDWARE-$ARCH.config.system.build.isoImage
# deploy -s .#$HOST-$HARDWARE-$ARCH --hostname $TARGET_IP
$ nix eval .#tests