Can you suggest a homemade oven cleaner?

With ovens, a little patience often works better than those extremely smelly and sometimes toxic commercial cleaners. To clean an oven overnight, put a cup or two of ammonia in a shallow pan and set the pan on a lower rack, toward the back of the oven. Close the door and leave overnight. The vapors will loosen the crud on the oven walls and floor. Scrub in the morning using a baking soda paste, then rinse. Another homemade cleaner left on overnight also works wonders. Mix 2 tablespoons dishwashing liquid, 2 teaspoons borax, 1/4 cup ammonia, and 1 1/2 cups warm water. Apply to the oven, let sit overnight, and then scrub in the morning. Always consult the owner’s manual for self-cleaning ovens to look for warnings about using these products.