Make carnitas: Trim fat from pork. Cut pork into 2- to 3-inch pieces; transfer to a 4-quart slow cooker. Stir in onion, orange juice, cumin, salt, oregano, and cayenne.
2
Cover and cook on Low 8 to 10 hours or High 4 to 5 hours.
3
Transfer pork to a large bowl; shred using 2 forks. Add enough cooking liquid from slow cooker to moisten.
