A few cups of feed...cover it with water and leave it be for a couple of days.
That is it.
Nothing more.
Except..make sure you have a large enough container, so that you don't have a mess to clean up if it decides to ferment so much it leaves the container! I don't think it is like making bread, where it expands so much, but fermentation will cause some expansion.
I don't use FF bc I know we would forget about it at times. Also, whenever it is hot out, my chickens won't eat the wet feed after a few hours, I think because it starts to ferment. I'll even add water to it bc they like it pretty wet, but they still won't eat it after a few hours in the heat. But, I guess mine are a bit picky that way!