Remove the top rack from the oven (to make room for the ham) and preheat oven to 300 degrees F.
Line a 9x13-inch baking dish or roasting pan with foil or coat with nonstick cooking spray and place ham inside cut-side down; set aside.
In a small bowl, whisk together maple syrup, brown sugar, dijon, cinnamon and nutmeg. Pour and brush mixture over the outside of the ham and place in the oven. Bake for 2 hours, brushing maple mixture on the ham every 30 minutes, or until ham reaches an internal temperature of 140 degrees F.
Carefully remove from oven, place ham on a serving platter and pour ham drippings through a strainer and into a medium saucepan. Whisk together cornstarch and water then whisk into drippings over medium-high heat. Continue cooking and whisking until sauce comes to a boil and reaches desired thickness. Remove from heat and serve over ham.