Preheat a gas or charcoal grill to medium-hot (375 to 425 degrees F).
Prepare the grill for indirect cooking: For a gas grill, turn off the center burner; for a charcoal grill, bank the coals on either side; place a drip pan under the grate between the heat sources.
Score a diamond pattern into the ham, about 1/8-inch deep into any fat.
In a small bowl, combine the coriander, paprika, cumin, cinnamon, and cloves. Rub the spice mixture over all sides of the ham.
Place the ham, flat side down, in the center of the grill over the drip pan. Cover and cook, adding briquettes to a charcoal grill as necessary to maintain the heat, until the internal temperature of the ham reaches 140 degrees F, 1 1/2 to 2 hours or 15 to 18 minutes per pound.
Meanwhile, in a small bowl, combine the marmalade, orange juice, and sugar. Double the glaze if you want extra to serve over top of sliced ham. Set aside 1/2 of the glaze for later.
Brush the marmalade mixture over the ham.
Cover and grill 5 minutes, until the glaze is lightly caramelized.
Remove the ham from the grill, transfer to a cutting board, and let rest 15 to 30 minutes.
Roasting instructions:
Preheat the oven to 400 degrees F. Position a rack in the lower third of the oven.
Score a diamond pattern into the ham, about 1/8-inch deep into any fat.
In a small bowl, combine the coriander, paprika, cumin, cinnamon, and cloves.
Rub the spice mixture over all sides of the ham.
Place the ham, flat side down, in a large shallow roasting pan and cook until the internal temperature of the ham reaches 140 degrees F, 1 1/2 to 2 hours or 15 to 18 minutes per pound.
Meanwhile, in a small bowl, combine the marmalade, orange juice, and sugar.
Brush the marmalade mixture over the ham.
Return to the oven and roast 5 minutes, until the glaze is lightly caramelized. Remove the ham from the oven, transfer to a cutting board, and let rest 15 to 30 minutes.
Notes
Treat your grill just like a oven. We have a gas grill so I heated it up to about 400 degrees using only the flames on the sides, turning the middle burners off. This creates a nice warm and toasty oven for your ham. Medium high heat is best. Too high and the sugars in the glaze can burn before the ham heats through.
If you don't have a grill you can also do this in the oven. Just heat oven to 400 degrees and place ham in the lower third of the oven.
Brush the glaze often – Apply the citrus glaze several times while grilling to build layers of flavor and a beautiful caramelized finish.
Make extra glaze – Reserve a small portion of the glaze (before brushing on raw ham) for drizzling over the cooked slices when serving.
Add a garnish – Top with a little orange zest or fresh herbs like parsley for a fresh, bright finish.
Use leftovers creatively – Grilled ham is amazing in sandwiches, salads, or breakfast scrambles the next day!