In a gallon-size zip-top bag, combine 1/2 cup cornstarch, garlic powder, salt and pepper. Add chicken, and shake well until all chicken is covered.

In a large skillet, heat coconut oil over medium heat. Add chicken pieces (working in batches if needed), and brown on one side for 30 seconds, flip and brown on other side for 30 seconds; drain. DO NOT skip this step.

In a small bowl, whisk hoisin, soy sauce, vinegar, pineapple juice, honey, garlic, ginger, cayenne and 2 tablespoons water together. Pour into slow cooker. Stir in bell pepper and green onions. Carefully add chicken to the sauce.

Cover and cook on low 4 hours.

Check chicken 25 minutes before serving. If the sauce has not thickened enough for serving, whisk together a slurry of 2 tablespoons cornstarch with 2 tablespoons cold water, and slowly stir it into the mix. Cover and cook for the remaining 25 minutes.

Serve over cooked brown rice.