*Optional*: Cut pork loin into 4 chunks. Heat the oil in a large pan until shimmery. Sear all four pieces of pork until each side is nicely browned. Do not cook all the way through.
Place seared (or raw) pork in a slow cooker with the garlic and onion. Season generously with salt and pepper. Whisk together the cumin, chili powder, oregano, chicken broth, lime juice, and orange juice. Pour the mixture over the pork. Cover, and cook on high for 4-6 hours or on low for 8-10.
Preheat the broiler on your oven. Remove the pork from the slow cooker, and shred with two forks (it should be very easy). Discard the onions and garlic, but reserve the liquid. Place the pork on a foil-lined baking sheet. Pour about 1/4 c. of the leftover liquid over the pork, and broil for 5-15 minutes, until crispy. Every 5 minutes, add another 1/4 c. of liquid and toss to ensure even crisping. Serve as desired!