Trim large pieces of exterior fat from the pork and cut the meat into 3 or 4 large chunks.
Arrange the sliced onion in the slow cooker, place the pork on top, and add the minced garlic.
Pour in the orange and lime juices, then add the cumin, oregano, paprika, pepper, salt, and bay leaves.
Cover and cook on low for about 8 hours or on high for approximately 5 hours until very tender.
Remove the bay leaves, shred the pork with two forks, and spread the meat across a baking sheet.
Spoon a little cooking liquid over the pork and broil for 4 to 6 minutes until some edges become crisp.