In a small bowl combine salt, cumin, chili powder, black pepper, oregano, cinnamon, and cayenne pepper.
Place the pork shoulder into the slow cooker. Rub the chopped garlic and seasoning mixture into the pork shoulder on all sides. Add lime juice, orange juice, beer, and salsa. Cover and cook on low for 8 hours or until the meat shreds easily.
Shred the meat using two forks. You can do this directly in the slow cooker or place it onto a cutting board, shred it and then return it to the slow cooker with the juice.
Preheat the broiler of the oven. Line a baking sheet with aluminum foil. Remove the shredded pork from the slow cooker and place it onto the baking sheet.
Pour a few spoonfuls of the sauce over the top of the meat on the baking sheet.
Place into the oven and broil for 5-10 minutes or until the edges of the pork are browned (keep an eye on it, you do not want to burn the pork).