Make the Sauce - In a medium bowl, whisk together maple syrup, pineapple juice, brown sugar, mustard, cinnamon, nutmeg, and cloves (if using).
Prepare the Ham - Pour half of the sauce mixture into a 6-quart slow cooker along with the ham placed cut-side down. Pour the rest of the sauce over the ham. For spiralized ham, place slices face up.
Cook Time - Cover and cook the ham for 3 to 4 hours on the low setting or until the internal temperature reaches 135 to 140ºF (57 to 60ºC) on a meat thermometer. The cooking time will depend on the size.
Rest the Meat - Transfer the ham to a cutting board. Cover with foil and allow it to rest for 15 minutes.
Make the Glaze - Add the juices and sauce at the bottom of the slow cooker into a saute pan. Cook over medium-high heat until the sauce bubbles. Stir occasionally until the mixture thickens and reduces to 1 cup, about 15 to 20 minutes.
Glaze the Ham - Brush some of the glaze over the round side of the ham. Allow it to set for 5 minutes, then brush another layer on the top.
Slice - Cut the ham into ¼-inch thick slices, if not already spiral cut. Serve with the remaining warm glaze on the side.
Notes
Serving Size: ½ pound boneless ham
Serving Per Person: ½ pound ham for boneless, ¾ to 1 pound for bone-in. For 10 guests, you would need a 5-pound boneless ham or around 7 ½ -pound bone-in ham.
Using a 6-quart Slow Cooker: A 5 to 7-pound ham works best.
Using Bone-in Ham: Spiral-cut, bone-in ham can be used instead of whole boneless ham. Add 1 to 2 hours of cooking time, depending on size.
For Larger Roasts: Increase cooking time to 4 to 5 hours for a 7 to 10-pound cut. A larger slow cooker may be needed, or trim the sides to fit the vessel.
Substituting Brown Sugar: Add more maple syrup, honey, orange marmalade, or apple jelly.