1 Preheat the oven to 325°F. Place the ham on a rack in a shallow roasting pan. 2  For a whole 10- to 15-pound ham, allow 18 to 20 minutes per pound; for a half--5 to 7 pounds--about 20 minutes per pound; or for a shank or butt portion weighing 3 to 4 pounds, about 35 minutes to the pound.