You can reheat the ham either in the microwave if you are heating up small amounts like slices. Another option is to reheat the slices in a frying pan. This creates a different flavor by caramelizing the glaze. If you have a large amount of ham to reheat you can heat it in the oven, place the ham in a baking dish and add about a 1/2 inch of water. Cover with foil and bake at 325 degrees for 15 minutes per pound.