Place cornstarch, black pepper and chicken chunks into a plastic bag. Shake until chicken is evenly coated with cornstarch.
In a large skillet, heat vegetable oil of medium-high heat. Add the chicken to the skillet and cook until chicken is browned on all sides, about 5 minutes. Chicken will not be cooked thru. Remove chicken from the skillet to the slow cooker.
In a small bowl, combine the hoisin sauce, soy sauce, honey, rice wine vinegar, garlic, ginger, pinch of red pepper flakes and sriracha. Stir until well blended. Pour over the chicken.
Stir the chicken until coated with the sauce. Turn the slow cooker to high and cover.
Cook for 3-4 hours until the chicken is cooked thru and the sauce is thick. Serve over rice.
Start checking the slow cooker at 2 hours. Depending on the size and power of your slow cooker, this dish may be done in less time.