I've never made my own catfish bait. I know I have read articles about it in the past, but I don't remember any recipe's. Seems like most of them started with a bread base (oatmeal, bread crumbs, cornflakes, etc.) and to that added an oily substance to hold it together, and there is always a stink ingredient (blood, guts etc.). I also seem to recall a lot of guys using anise oil or anise root.
I think most of them boiled the mixture and let it "cook down" for the desired consistency.
It could be fun trying different mixtures.
You might search for articles online about catfishing.