Trim excess fat from pork shoulder if needed, but leave a little for flavor. Pat dry and rub pork thoroughly with Okie Rub, salt, and brown sugar. Let sit at room temp for 15–30 minutes if time allows—this boosts flavor and tenderness.
Scatter sliced onions across the bottom of your slow cooker. Place the seasoned pork shoulder on top. Pour in apple cider vinegar and broth around the sides (don’t rinse off the rub!). Cover and cook on low for 8–10 hours or on high for 5–6 hours, until the pork is fall-apart tender and easy to shred.
Shred pork with two forks (I prefer to shred it within the crockpot for less mess, just be careful as the juices are hot or wear gloves to protect against any splatters. OR you can transfer meat to a cutting board to shred, then return meat to it's juices). Discard excess fat, if necessary.
Add BBQ sauce. Toss to coat. Taste and adjust seasoning or add extra sauce if desired (you can also add a splash of hot sauce or Worcestershire sauce)! Serve hot on toasted buns, baked potatoes, nachos, or BBQ plates with slaw.
