Drizzle oil in the bottom of the slow cooker. Place the onion on top.
Make the rub: In a small bowl combine garlic powder, onion powder, chili powder, paprika, mustard powder, salt, pepper, vinegar and honey.Mix until it forms a paste.
Place the roast in the slow cooker on top of the onions. Pour the spice mixture on top of the roast. Use your hands or a rubber brush to make sure the whole roast gets covered in the sauce.
Slow cook: Cover and cook the roast on low for 8-10 hours or high for 6 hours.
Shred the meat in the slow cooker using tongs or two forks.
Make sandwiches: Toast buns then top with coleslaw, pulled pork and barbecue sauce. Enjoy!