Grease a 6-quart slow cooker with cooking spray.
Layer sliced onions in bottom of cooker.
Pat pork roast dry with paper towels.
Mix seasoning blend and salt; rub all over pork.
Place seasoned pork on top of onions.
Pour broth AROUND roast (not over top).
Cover and cook on HIGH 6-7 hours or LOW 9-10 hours.
Meat should pull apart easily with fork when done.
Remove and let rest 10 minutes.
Shred meat, removing any large fat pieces.