01 - Place the chicken breasts in an even layer across 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 well coated.
04 - Cover the slow cooker and cook on High for 4 hours or on Low for 6 to 7 hours, until the chicken is tender and reaches an internal temperature of 165°F.
05 - Remove the chicken from the slow cooker and transfer to a cutting board or 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. Pour the slurry into the sauce remaining in the slow cooker and stir to incorporate.
07 - Return the shredded or whole chicken to the slow cooker and stir to coat evenly. Cover and cook on High for an additional 15 to 20 minutes until the sauce has thickened. Serve hot over rice, quinoa, or steamed vegetables, garnished with chopped parsley or green onions.