Rinse and pat dry the pork roast. Stir together the olive oil, salt, pepper, oregano, and cumin. Rub the spice mixture all over the pork roast. Place the roast in the slow-cooker with the fat cap facing up. Place the onions and the garlic over the roast. Pour the orange juice over the roast.
Cover with lid and cook on LOW for 9-11 hours, until tender and falling apart. (If the fat cap is still intact over the roast, pull the biggest pieces of it off and discard.) Carefully pull apart the roast, leaving plenty of bite-size chunks of meat. (Try not to shred it to tiny pieces.) Use a slotted spoon, spatula, or tongs to lift the meat out of the slow-cooker.
Heat a large non-stick skillet over high heat. Place about 2 cups worth of shredded pork into the hot pan and press down with a spatula. Cook until the bottom side of the pork is crispy and browned, about 2 minutes.
Transfer to a platter or serving dish and drizzle with some of the juices from the slow-cooker. Repeat with the remaining pork. Enjoy!
FREEZER INSTRUCTIONS: If you are freezing extra pork or making the recipe in advance, skip the stove-top cooking step and simply place the shredded pork in a gallon size zip-close bag along with the crock-pot juices. When ready to use, thaw completely in the refrigerator and then use the above directions to crisp the pork in a pan on the stove.