An aluminum tray we placed on the bottom to help keep it clean welded onto the surface. There is an aluminum warning embossed in practically the same color.  So, we had to buy another oven bottom within a month of purchase. Also, many slide-in oven manufacturers' have trim kits available to make the sides and back of their ovens look built-in and keep crumbs and liquids from spilling into the gaps. Frigidaire (manufacturer Electrolux) doesn't!