01 - In a small bowl, combine salt, pepper, smoked paprika, garlic powder, onion powder, dried oregano, and brown sugar. Rub the mixture evenly over the beef chuck roast.
02 - Place sliced onions and minced garlic in the bottom of a slow cooker. Set the seasoned beef on top.
03 - In a jug, mix together beef broth, barbecue sauce, apple cider vinegar, and Worcestershire sauce. Pour over the beef.
04 - Cover and cook on low for 8 hours, or until the beef is tender and easily shreds with a fork.
05 - While the beef is cooking, prepare the slaw: In a large bowl, whisk together mayonnaise, apple cider vinegar, honey, celery seed if using, salt, and pepper. Add shredded cabbage and carrots, tossing to coat evenly. Chill until serving.
06 - When the beef is done, transfer to a large bowl and shred using two forks. Skim excess fat from the cooking liquid, then return shredded beef to the slow cooker and mix with juices.
07 - Pile pulled beef onto the bottom half of each bun, top with a generous spoonful of slaw, and finish with the bun tops. Serve immediately.