How to apply nixpkgs patch before PR lands in channel

Is it possible to apply patches to nixpkgs in Snowfall Lib?

Something like:

lib.mkFlake {
      channels.nixpkgs = {
        input = inputs.nixpkgs;
        patches = [
          (inputs.fetchpatch {
            url = "https://patch-diff.githubusercontent.com/raw/NixOS/nixpkgs/pull/370304.patch";
            sha256 = lib.fakeSha256;
          })
        ];
        config.allowUnfree = true;
      };
...

Or how would I apply patches to nixpkgs before they land in the stable/unstable channel?

Start by reading the Snowfall Lib documentation for lib.mkFlake and channel configuration, then check how nixpkgs inputs and fetchpatch are handled. Done means documenting whether and how users can apply a nixpkgs patch before it reaches a channel, including a supported configuration example.