In a small bowl place oregano, cumin, black pepper, salt, chili powder,and cinnamon, then mix thoroughly.
Put the pork shoulder in the slow cooker and add the onion, garlic, limes, bay leaves, water and spice mixture.
Cover and cook for 6 hours on high. Flip over every couple hours in the slow cooker. Check after 5 hours or so and cook until it separates easily with a fork.
Heat oven on broiler.
Move meat to a large cutting board and using two forks begin the shred the meat.
Place the meat in a single layer on a baking tray, and broil for about 5 minutes.
Serve with flour or corn tortillas, lettuce, tomato, sour cream and hot sauce.