Add the 6-8 lbs bone-in spiral sliced ham to your slow cooker. Melt ¼ cup butter and ½ cup honey in a saucepan on the stove or in the microwave. Pour the melted butter and honey mixture over the ham.
Cover with lid and cook on low for 3-4 hours. In the last 15 minutes, line a baking sheet with foil.
In the last 30 minutes, mix together the glaze: In a saucepan, heat up mix 1 cup brown sugar, 1 tsp onion powder, ½ tsp cinnamon, ½ tsp salt, ¼ tsp ground black pepper, ¼ tsp ground nutmeg, and ¼ tsp ground cloves with ½ cup water. Heat for 30 seconds until the sugar dissolves.
Preheat the oven to “broil” setting. Next, place the ham on the baking sheet and brush half of this brown sugar glaze over the ham. Broil for 1-2 mins until sugar carmelizes, then remove from the oven.
Brush the ham with the last half of the brown sugar glaze. If they glaze is too thick, just stir in 1-2 Tbsp of water to help loosen it. Now it’s ready to serve!