Next, in a small bowl whisk together the honey and melted butter. Rub the mixture all over the ham, making sure to get in-between the slices. Cover with the slow cooker lid and cook on low for 4-5 hours or until the internal temperature of the ham reaches 140 degrees F.
20 minutes before the 4 hours is up, move the oven rack to the middle position and preheat the broiler to high. Then, line a roasting pan or rimmed baking sheet with foil. In a small bowl whisk together the sugar, onion powder, cinnamon, nutmeg, paprika, cloves, and allspice.
BROIL THE HAM:
Next, transfer the ham to the prepared baking pan, and rub half of the sugar mixture over the top of the ham.
Watch the ham closely while you broil it for 5-10 minutes, or until bubbly and caramelized, and then remove the ham from the oven. Keep the broiler on.
MAKE THE HAM GLAZE:
In a small saucepan add the rest of the sugar mixture and 3 tablespoons of ham juices from the slow cooker. If there are not enough of the ham juices, then you can use 3 tablespoons of water. Set the heat to medium-high and bring the mixture to a boil. Take the sugar mixture off of the heat after it boils for 1 minute.
BROIL THE HAM AGAIN:
Use a pastry brush to brush the glaze all over the ham.
Watch the ham carefully while it is under the broiler for 1-4 minutes. Then, remove the ham from the oven and let it rest under loose foil for 15 minutes.