1 cup or more baking soda
A squirt or two of liquid detergent
Sprinkle water generously over the bottom of the oven, then cover the grime with enough baking soda that the surface is totally white. Sprinkle some more water over the top. Let the mixture set overnight. You can easily wipe up the grease the next morning because the grime will have loosened. When you have cleaned up the worst of the mess, dab a bit of liquid detergent or soap on a sponge, and wash the remaining residue from the oven. If this recipe doesn’t work for you it is probably because you didn’t use enough baking soda and/or water.