I've seen some very elaborate expensive setups in studios dedicated to food. But to shoot single plates straight down all you need is a large copy stand capable of holding a 4x5 with a right angle viewing back. Any decent carpenter could build a functional one if you don't own the official variety. Old vertical-column LF enlargers make excellent copystand devices if you alter them. I don't see many shots of a whole table of food taken straight down. Those are mostly done on an angle; so you'd wouldn't need anything special to do that.