Combine garlic powder, oregano, cumin, coriander, cinnamon, crushed red pepper, and salt in a small bowl. Season pork with mixture, rubbing to coat all sides thoroughly.
Store seasoned pork in refrigerator overnight (or proceed directly to next cooking steps).
SLOW COOKER METHOD
Place sliced onions in bottom of slow cooker. Add bay leaves. Place pork on top.
Juice the two oranges and two of the limes directly into the slow cooker.
Cover and cook on low in slow cooker for 8-10 hours.
Remove pork from slow cooker and place onto a large platter. Shred pork. Next, follow directions for last step – crisping (see below).
Preheat the oven to 300F.
Place the onions and bay leaves in a layer in the bottom of a roaster or large oven safe Dutch oven. Place pork on top, and juice two limes and two oranges over the pork.
Cook covered for 3 hours, then flip the pork over and cook for 2 more hours. You’ll know it’s done when it’s fork tender (target range is 145F-160F).
Remove pork from pan and place onto a large platter. Shred pork. Next, follow directions for last step – crisping (see below).
Spoon some of the pork cooking juices over the shredded pork.
Preheat oven to broil. Place some of the pork (the portion you are serving for that meal) onto a baking sheet. Cook for 3-4 minutes until slightly crispy.
Or in skillet:
Set a skillet over medium heat. When the pan is very hot, add the pork, spreading it out evenly over the bottom of the pan. Cook undisturbed for a couple of minutes, until it is richly browned and releases itself from the bottom of the pan. Gently turn the pieces to brown the other side. Remove to a plate lined with paper towels. Sprinkle with salt (preferrably coarse salt for most flavor impact!).