Place garlic, lime juice, oil, salt, black pepper, oregano, onion powder, cumin, peppers, and adobo sauce in a small food processor. Pulse until well combined, and a paste is formed.
Rub the pork shoulder with the chipotle paste, rubbing it thoroughly on all sides. If time allows, let the pork marinate for 30 minutes up to overnight. If not, go to the next step.
Place orange juice, chicken broth, bay leaves, and seasoned pork shoulder into a slow cooker. Cook for 8 hours on low or 4 hours on high, until internal temperature reaches 145 °F on a food thermometer. The pork should be so tender that meat falls apart easily.
Remove pork from the slow cooker and shred the meat using two forks, removing excess fat. Taste and adjust seasoning if needed.
Heat oven to broil. Line one baking sheet with foil and spray with cooking oil.
Place carnitas onto a baking sheet with a cup or so of the juices and broil until most pork looks golden, crisp, and crusted about 4 minutes. Remove from oven.
Garnish carnitas with chopped cilantro, if desired.