Place pork on a large plate. Brush oyster sauce over all sides.
In a small bowl combine paprika, garlic powder, onion powder, and black pepper. Stir to combine.
Sprinkle and rub the spice mixture evenly over all sides of the pork.
Cover and refrigerator for at least 3 hours or overnight.
To cook, place pork in a slow cooker and set to low. Cook until pork is tender, about 9 hours.
Pour off juices into a small bowl, and strain out any visible fat. Pour juices back into the slow cooker and using two forks pull the pork apart. Ready to serve.
