Preheat oven to 325°F
Remove ham from packaging
Place ham cut-side down in a roasting pan
Score the surface in a diamond pattern if desired
Add 1/2 to 1 cup water to the pan
Cover tightly with foil
Bake until heated through, about 15 to 18 minutes per pound
Remove foil during the last 20 to 30 minutes if glazing
Brush with glaze if using
Continue baking until glaze is set and internal temperature reaches 140°F
Remove from oven
Let rest 10 to 15 minutes before slicing
Slice and serve