Rinse and dry the pork shoulder. Sprinkle with salt and freshly cracked black pepper.
In a small bowl, stir together the oregano, cumin and chili powder with olive oil and rub all over the pork. Place the pork in a slow cooker and top with the onion and garlic. Squeeze the juice of the 2 orange over the pork, and pour in the salsa. Cover and cook on low for 8 hours or on high 4 hours.
Once the meat is tender, remove from slow cooker and let cool slightly before pulling apart with two forks. Return to the slow cooker and pour juices over the pork.
Serve the pulled pork on burger or sandwich buns and enjoy!