Pour the cider into a 6-quart slow cooker. In a small bowl, combine the maple syrup, Dijon, ginger and pepper. Zest the orange into the bowl and mix the marinade ingredients together.
Rub the marinade onto one side of the ham and place it marinade-side-down into the slow cooker. Spoon the rest of the marinade all over the rest of the ham.
Peel the orange and coarsely chop the pulp, discarding any seeds. Add the orange around the sides of the ham and tuck the cinnamon stick inside too.
Cover the slow cooker and cook on low for 8 hours or on high for 4 hours.
To serve, transfer the ham to a platter. Cover to keep warm. Strain liquid from the slow cooker into a gravy pitcher and serve with the ham.
Notes
*If you are preparing this recipe as gluten-free, just be sure to use brands of apple cider, maple syrup, mustard and ham that are known to be GF.