Flickr: Wolf Rock. For god's sake, this is simple. A pizza is cooked in a pizza oven, not a pizza skillet. So to reheat pizza, you attempt to replicate a pizza oven. Place a baking sheet in your oven, blasting the heat as high as your oven will go. Once the baking sheet is hot, place the pizza on it. The bottom will be crispified by the hot baking sheet.