The best alternative to use for aluminum foil depends on what you are using it for. If your goal is to keep your oven clean, try placing your baking dish inside a larger baking dish during cooking. The second dish will catch any drips from your recipe and your oven will have the air flow it needs to perform its best. You should never place anything on the bottom of your oven. You could also place a silicone mat or baking tray on the lower rack of your oven, rather than a sheet of foil. Just make sure there are at least three inches of space between the mat and the walls of your oven to allow the heat to flow freely.  Silicone oven liners should be used with caution. Never place a silicone oven liner at the bottom of your oven. They should not be used in gas ovens. If you are looking for an alternative to line your baking pan or cookie sheet for easier cleanup, parchment paper is a good solution. Parchment paper is safe up to 425 degrees and is non-stick and non-reflective. It does well in baking dishes as it won’t scratch the surface. Be careful not to use parchment paper when broiling or over any open flame.