Combine the rub ingredients together in a small bowl. Use your hands to apply the rub over the entire surface of the pork.
Place the pork butt in the slow cooker, fat side up. Add the oranges, carrots, onion and bay leaves and pour the chicken stock (or orange juice) over and cover.
Slow cook on low heat for 10 hours, or high heat for 6 hours.
Use a slotted spoon to carefully transfer the pork carnitas to a serving platter. Allow the meat to cool slightly, then shred by hand or by using two forks. Eat as is, but BEST if crispy.
Crispy
Remove and discard cooked orange and vegetables from cooking liquid. Set aside.
In a large skillet over high heat add a tablespoon of oil and fry shredded carnitas meat in batches, pouring 1/4 cup of cooking liquid in and simmer until juices have evaporated and meat is crispy and caramelized.
Serve with hot tortillas, refried beans, sliced onions, tomato slices, cilantro, limes and salsas of choice.