Place the raw pork in the slow cooker. Stab the pork 8 or 9 times with a knife about ½ way through the meat.
Rub the pork shoulder with the chili powder, cumin, oregano, cinnamon, and salt. Place the bay leaves on top of the meat, and toss the onion into the crock pot ( I usually place two of the quarters on top of the meat and two next to the meat in the pot ).
Stir the mixed garlic into one of the juices, and then pour all of the juice combined with the garlic, plus the chicken broth into the pot.
Cover and cook on high for 5 hours or low for 8.
After cooking, remove the bay leaves and the bone from the slow cooker pot and shred all of the remaining meat. This is a great point at which to let the meat cool and refrigerate or freeze it to have later.
Immediately before serving the meat ( defrost in the fridge first, if you'd frozen it ), place the shredded meat in a thin layer on a jelly roll pan or other broiler-safe pan with sides. Broil on High for 5 to 7 minutes, or until edges of the shredded meat start to brown and crisp.