01 - Place the chicken breasts in an even layer on the bottom of the slow cooker.
02 - In a medium bowl, whisk together the honey, soy sauce, ketchup, hoisin sauce (if using), minced garlic, grated ginger, vinegar, black pepper, and red pepper flakes until well combined.
03 - Pour the sauce mixture evenly over the chicken breasts, ensuring they are fully coated.
04 - Cover and cook on High for 4 hours or on Low for 6 to 7 hours, until the chicken is tender and cooked through.
05 - Remove the chicken from the slow cooker and transfer to a plate. Shred using two forks, or leave the breasts whole if preferred.
06 - In a small bowl, stir together the cornstarch and cold water to form a slurry. Stir the slurry into the sauce remaining in the slow cooker.
07 - Return the shredded or whole chicken to the slow cooker. Stir to coat evenly, cover, and cook on High for an additional 15 to 20 minutes until the sauce has thickened.
08 - Serve hot over rice, quinoa, or steamed vegetables, garnished with chopped fresh parsley or green onions.