Heat the oven to 400°F and oil a rimmed sheet pan. Mix chicken, egg, breadcrumbs, milk, scallions, garlic, ginger, salt and pepper just until combined, then shape into 24 equal meatballs about 1 1/2 inches across.
Bake meatballs for 10 to 12 minutes until their outsides are firm enough to lift; they are not fully cooked yet. Meanwhile, bring sweet chili sauce, broth, soy sauce and vinegar to a simmer in a saucepan.
Pour hot sauce into a 6-quart slow cooker and add red pepper. Transfer the hot partially cooked meatballs directly into the sauce, cover immediately and cook on low for 2 1/2 to 3 hours until the largest meatball reaches 165°F.
During the final half hour, bring rice and its measured water to a boil in a saucepan. Cover and cook on low for 18 minutes, then rest off the heat for 10 minutes.
Turn meatballs gently through the sauce without breaking them. Divide rice among 6 plates and add 4 meatballs, red pepper and sauce to each serving.