In the bowl of a food processor or blender, blend together the cherries, brown sugar, maple syrup, dijon mustard, and garlic powder until smooth.
Spray slow cooker with non-stick cooking spray. Add about ¼ of the glaze to the bottom of the slow cooker.
Add the ham and pour the glaze over the top, ensuring that you get some of the glaze in between the layers.
Cover, cook on low for 2-3 hours, until heated through.
OPTIONAL: Take 1 Cup of the glaze from the slow cooker after the ham is cooked. Pour into a medium saucepan and bring to a simmer over medium heat. Stir together the cornstarch and cold water. Whisk into the glaze until thickened. Remove from the stove and serve with the cooked ham.