Preheat conventional oven to 350°F. Place fully cooked boneless ham on a rack inside of a deep, oven-safe cooking pan. Fill bottom of pan with 3-4 cups of water. Tightly cover ham with aluminum foil. Heat ham to an internal temperature of 145°F. Approximately 15 minutes per pound.
Discard aluminum foil and add Brown Sugar Glaze if desired. Heat for additional 30 minutes at 350°F with glaze.