What many slice vendors do is to fully bake the pizzas, place them onto aluminum serving/display trays and store them in the heated (145F) cabinet with approximately 70 to 75% R.H. (relative humidity). Under these conditions the pizza will hold up well for about 2-hours, but the cheese will begin to look something like a melted blob of plastic (ain't much that can be done about that). Then. when a slice is ordered, the slice is removed from the cabinet and placed into an oven for warming/re freshening. The type of oven that seems to work the best is a small counter top conveyor oven, but I've seen deck ovens used to great success too as well as toaster ovens for use at bars where time is not a great issue. The reheating process brings the cheese back to a level of life, but if you give the slice a very light sprinkle of additional cheese as you put it into the warming oven it restores the slice to that fresh baked appearance again.
Tom Lehmann/The Dough Doctor