Rub garlic, seasoning salt, black pepper, and cayenne pepper onto roast.
Place roast in a large Dutch oven; fill halfway with water. Add onion; bring to a rolling boil over high heat. Reduce heat; simmer until meat falls off the bone, 3 to 4 hours (depending on the size of the roast).
Place hot roast in a serving bowl. Pour in barbecue sauce; stir until well combined. Serve on buns.
Faye's Pulled Barbecue Pork · Dinner Match Lab | Dinner Match Lab