Add the pork shoulder chunks, onion, garlic, cumin, oregano, chili powder, orange juice, salt, and black pepper to the slow cooker. Stir to coat the meat evenly.
Cover and cook on low for 8 hours until the pork is very tender and pulls apart easily with a fork.
Remove the pork from the slow cooker and shred it with two forks, discarding any large pieces of fat. Return the shredded pork to the slow cooker and stir it into the juices.
In a mixing bowl, combine the shredded cabbage, shredded carrot, mayonnaise, lime juice, and cilantro. Toss until the vegetables are evenly coated.
Warm the corn tortillas in a dry skillet or microwave. Fill each tortilla with pulled pork and top with a scoop of fresh slaw.