Spray a large slow cooker insert with cooking spray. (I use a 7 quart size).
Remove ham from wrapper and place in the bottom of prepared slow cooker. Stir together melted butter and honey then drizzle all over ham and inside ham slices. Cover with lid and cook on low heat 3 to 4 hours.
In a medium bowl, add sugar, onion powder, cinnamon, nutmeg, ginger and cloves. Stir to combine. Sprinkle HALF of this mixture all over the cooked ham. At this point you can cover again and let sugar mixture caramelize while in the slow cooker for another 30 to 45 minutes.
OR you can very carefully, using oven mitts, remove slow cooker insert to oven and place under broiler for 1 to 2 minutes. (*ONLY the insert, not the entire slow cooker*) I placed mine under the broiler for 2 minutes and it carmelized perfectly!
Carefully remove from oven and place insert back inside crock pot and cover with lid. Turn off heat.
Meanwhile, pour the remaining sugar mixture in a small saucepan. Add 3 Tablespoons water. Stir and let come to a boil over medium heat. Remove from heat and pour glaze all over ham.
Slice and serve ham warm. Enjoy!