To heat up a pre-cooked spiral ham, cover the entire mass with foil. Place it and oven preheated to 275 degrees Fahrenheit and let the meat warm for about 10 minutes per pound. To keep the ham moist, put a shallow water-filled pan on a lower rack.
If there is a glaze, spread it over the meat, and put the ham back into the oven at 400 F for 10 to 15 minutes. In either case, after removing the ham from the oven, let it rest for 10 minutes. Heat individual slices of ham using the same oven method. Alternately, slices warm well in a skillet. Spiral-cut hams are also fine when served cold or room temperature.