In a bowl, mix together the cumin, oregano, salt, black pepper, and cayenne pepper. Rub the spice mixture all over the pork shoulder pieces.

In a skillet over medium-high heat, heat the vegetable oil. Brown the pork pieces on all sides, about 5-7 minutes.

Transfer the browned pork to the slow cooker. Add the chopped onion, minced garlic, orange juice, and lime juice.

Cover and cook on low for 6-8 hours or on high for 3-4 hours, until the pork is tender and shreds easily.

Remove the pork from the slow cooker and shred it with two forks. Return the shredded pork to the slow cooker and mix with the juices.

Serve in tacos, burritos, or with rice. Enjoy!