One of the easiest ways to clean your oven is to make your own foam. All you need to do is to get some vinegar and baking soda together and it will froth like crazy.
These compounds together make a great oven cleaner that is natural and much less harsh than oven cleaners you can buy at the store.
To clean your oven wipe it down with water, then sprinkle baking soda over the whole surface for a few hours. After that add your vinegar to a spray bottle and wet the vinegar. You will see it start to foam immediately. This foaming action removes all of the stuck on things left in the oven. Wipe everything clean with a damp sponge and your done.