01 - Spread the chopped onion and minced garlic evenly across the bottom of the slow cooker insert.
02 - Nestle the trimmed beef chuck chunks on top of the onion and garlic layer.
03 - In a small mixing bowl, whisk together the chopped chipotle peppers, lime juice, ground cumin, dried oregano, smoked paprika, salt, black pepper, apple cider vinegar, and beef broth until well combined.
04 - Pour the sauce mixture evenly over the beef, then tuck the bay leaves into the liquid. Cover and cook on low for 8 hours, or until the beef is fall-apart tender and shreds effortlessly with a fork.
05 - Discard the bay leaves. Using two forks, shred the beef directly in the slow cooker, mixing it thoroughly with the accumulated juices to absorb maximum flavor.
06 - Serve the barbacoa hot with warm tortillas, over steamed rice, or in burrito bowls with your choice of toppings.