Place ham in slow cooker. Cover, and cook on low for 1-2 hours.
While ham is cooking, whisk together juices and cornstarch in a saucepan.
Stir in about half of the jam and half of the cranberry sauce. Cook and stir until hot and bubbly. Add butter and stir in remaining jam and cranberry sauce.
Spoon glaze over ham after it has cooked for 1-2 hours.
Cover and cook for 2 more hours on low.
Slice ham and serve.