How do I make an oven cleaner?

Ketchup! Paint it on and let it sit overnight.The acids break down all the gunk

LOTS of homemade recipes: http://www.swagbucks.com/?f=11&q=diy+oven+cleaner

I'm the caretaker/mgr of a housing complex and it seems very few ever leave stoves and ovens as clean as they should be. TSP (trisodium phosphate) by far works best (and no smell) better than any oven cleaners I've tried . I use a plastic ice cream pail 2/3 filled with hot water and add a teaspoon of TSP then apply liberally and let set for several minutes and scrub with Scotchbrite pad. In some cases the grease is so thick I use a plastic putty knife to scrape off he loosened grease before I use a scrubbing pad. I've cleaned over a 100 stoves using this method. The stoves look like new when I'm finished.

I should have mentioned I use a lot of paper towels to wipe up the first layer of goo and try to keep my initial water as clean as possible. I also soak the stove hood filter in TSP and rinse under the faucet with hot water gets the filters clean w/o any effort.

Warm the oven 5 minutes, make a mixture of a cup of vinegar and baking soda, apply with an old sponge and wipe after an hour. Works for me!