Workflow for creating Reshade compatible lut from images?

I'm interested in trying out luts taken from films for the game versions I'm currently playing but cant figure out exactly how this works

Is there a quick and easy way to generate a reshade compatible lut from a screencap of a film for example? I feel like this should be straight forward but I cant get my head around it, or the formats of the already made luts are different than reshades.

This should get you started: reshade.me/forum/shader-discussion/3179-...correction-the-guide