1. Combine pork, panko, scallions, egg, soy sauce, ginger and garlic in a large bowl; mix gently but thoroughly with your fingers. Roll into 1-inch balls.
2. Mist slow cooker with nonstick cooking spray. Add meatballs. In a small bowl, whisk together barbecue sauce, plum sauce and hoisin sauce; pour over meatballs. Gently stir to coat.
3. Cover and cook on low until meatballs are cooked through, 3 to 5 hours.