Preheat oven to 325°F.
Place the ham on a cutting board. With a sharp knife, score the top of the ham. Start at one end of the ham and make a cut about 1/3-inch deep into the ham. Continue scoring, leaving about an inch between each cut.
In a medium bowl, combine the apricot preserves, honey, mustard, and orange marmalade. Stir until combined.
Place the scored ham in a roasting pan.
Pour half the apricot glaze (about 3/4 cup) on top of the ham. Cover with aluminum foil.
Roast for 15 minutes per pound of ham (about 2 hours for an 8-pound ham), basting occasionally throughout.
A few minutes before removing the ham from the oven, heat the remaining glaze in a small saucepan until heated through (3-5 minutes).
Remove the roasted ham from the oven (the internal temperature should read 145°F). Baste the glaze over the roasted ham. Let the ham rest for about 15 minutes before slicing.