Spray a 6-quart slow cooker with nonstick cooking spray.
Place ham, flat side down, inside the slow cooker. Pour water around the base of the ham.
In a small mixing bowl, whisk together maple syrup, honey, mustard, cinnamon and nutmeg then pour on top of ham. Cover and cook on low for 6-8 hours.
When ham is done cooking, remove it from the slow cooker and cut into slices. Pour ham drippings through a strainer and into a medium saucepan.
Whisk together 2 Tablespoons cornstarch and 2 Tablespoons of water then whisk into drippings over medium- high heat.
Continue cooking and whisking until gravy comes to a boil and reaches desired thickness. Serve gravy with ham.