Place ham on rack in a shallow roasting pan. Bake, uncovered, at 325° for 30 minutes.

Score top of ham in a diamond pattern, and stud with cloves. Combine orange rind, juice, brown sugar, and mustard; spoon half of mixture over ham. Bake 15 minutes.

Spoon remaining orange mixture over ham. Bake an additional 15 minutes, basting frequently with pan drippings. Remove ham to a serving platter. Garnish with orange slices, if desired. Slice and serve hot.