Place the pork shoulder, oranges, onion, garlic, kosher salt, cumin, black peppercorns, and bay leaves into a large Dutch oven. Add water to cover. Bring to a boil over high heat, then reduce the heat to medium-low, and simmer for 10 minutes. Skim off any foam that rises to the top. Cover loosely, and simmer until the meat is tender, about 1 1/2 hours. Allow the pork to cool, covered, in the broth for 1 hour. Shred the meat with two forks.