When freezing cooked lasagna, you need to ensure that it is completely cooled down before storing it and cover it properly with layers of plastic wrap. It is not advised to freeze it in the dish that it was baked in but rather remove it and place it into a foil dish or cut individual portions and store those separate from each other. When freezing uncooked lasagna, it is suggested that you assemble the lasagna in a foil dish and freeze the whole thing as it will loose its form otherwise.