I have a silicone or teflon sheet for the bottom of the oven.
It's wonderful for catching spills and cleans up easily. It's so much easier than cleaning the oven.
We put a new oven in our cottage and the element is below the bottom of the oven. You can't use one of these sheets on the bottom of an oven if the sheet is above the element, because it blocks the heat and the element can be damaged. You can, however, put it on the bottom shelf which allows air flow above the element.
A friend of mine ordered one of these from a mail order catalog, but I found them at Bed Bath and Beyond.