Rinse and dry the pork shoulder. Salt and pepper liberally. Mix the oregano and the cumin with olive oil and rub all over pork. Place the pork in a slow cooker and top with the onion, garlic, and jalapeno. Squeeze over the juice of the orange and add the two halves. Cover and cook on low for 8 to 10 hours or on high 4 hours.
Once the meat is tender, remove from slow cooker and let cool slightly before pulling apart with a fork. In a large saute pan, heat the vegetable oil over high heat. Press the carnitas into the oil and fry until crusty on one side. Serve.