01 - Scatter the sliced onions and minced garlic across the bottom of the slow cooker insert, creating an even aromatic bed for the roast.
02 - Combine the smoked paprika, chili powder, ground cumin, salt, black pepper, and cayenne pepper in a small bowl. Rub the spice mixture evenly over all surfaces of the trimmed beef chuck roast, pressing gently to adhere.
03 - Place the seasoned beef chuck roast directly on top of the onion and garlic bed in the slow cooker.
04 - Pour the barbecue sauce, beef broth, apple cider vinegar, and Worcestershire sauce evenly over the roast, allowing the liquids to pool around the base.
05 - Secure the lid and cook on the low setting for 8 hours, or until the beef is fall-apart tender and shreds effortlessly with a fork.
06 - Carefully remove the roast from the slow cooker and transfer to a large cutting board. Use two forks to pull the meat apart into coarse shreds, discarding any large pieces of fat or gristle.
07 - Return the shredded beef to the slow cooker and stir thoroughly to coat with the cooking liquid. Cover and continue cooking on low for 15 to 20 minutes, allowing the meat to reheat and absorb additional flavor.
08 - Pile the pulled beef generously onto burger buns and top with coleslaw, or serve over rice or in lettuce wraps for a lighter option. Drizzle with extra barbecue sauce as desired.