In a small bowl, mix together the cumin, chili powder, smoked paprika, oregano, garlic, salt, and pepper. Rub this spice mixture all over the pork chunks.
Place the quartered onion at the bottom of the slow cooker and lay the seasoned pork on top.
In a separate bowl, combine the orange juice, lime juice, and chicken broth. Pour this mixture over the pork.
Cover the slow cooker with the lid and cook on low for 8 hours or on high for 4 hours until the pork is tender and easily shredded.
Once cooked, remove the pork from the slow cooker and shred it with two forks.
If desired, place the shredded pork on a baking sheet and broil in the oven for 5-7 minutes to achieve a crispy texture.
Serve the carnitas warm, garnished with fresh cilantro, alongside warm tortillas and your choice of toppings (like diced onions, salsa, or avocado).
Notes
For extra crispiness, broil the shredded pork after cooking.