Pat the pork shoulder dry and trim away any excess fat.
Combine the brown sugar, smoked paprika, garlic powder, onion powder, chili powder, salt, and pepper.
Rub the pork with olive oil and coat it with the spice mixture.
Add sliced onion and minced garlic to the bottom of the crockpot.
Place the seasoned pork on top.
Whisk together the barbecue sauce, chicken broth, apple cider vinegar, Worcestershire sauce, mustard, and brown sugar.
Pour the sauce over and around the pork.
Cover and cook on LOW for 8–10 hours or HIGH for 4–6 hours, until the pork is very tender.
Transfer the pork to a bowl and shred it with two forks.
Return the shredded pork to the crockpot and mix with the cooking juices.
Let it sit for 10–15 minutes before serving.