How long do I preheat my Flat Top? You will want to preheat the grill for approximately 20-25 minutes with the Flat Top in place. Related articles How do I season my Flat Top? It is recommended that I brush food with oil before cooking, what if I can’t (eggs, pancakes, etc.)? Why do I season my Flat Top? How do I clean my Flat Top? How long do I preheat my Glazed Baking Stone?