Found this on the web. Good luck
The method you use to remove this difficult mess will depend on the interior finish of your oven and whether it is gas or electric or has a self-cleaning or continuous-cleaning feature.
For a regular electric oven: Place a bag of ice directly on the melted plastic to chill it and make it more brittle. Then carefully, using a razor-blade scraper, lift off the puddle of plastic. This procedure will not hurt an interior porcelain finish.
For a regular gas oven: First turn off the gas. Then take out the bottom panel (there should be two screws in the back that can be removed to lift out this base plate). If it fits, put the panel in the freezer until the spilled plastic becomes brittle enough to scrape off, or use the bag-of-ice technique, keeping the panel flat on a kitchen counter.
For an oven with a self- or continuous-cleaning feature: Turn on the oven to its lowest setting and heat only until the plastic becomes pliable. Then use a wooden spatula or spoon (other materials may damage the surface) to remove the melted plastic.
As a last resort, it may be necessary to replace the floor or bottom plate in your oven.