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 fully coated.
04 - Cover the slow cooker and cook on High for 4 hours or on Low for 6-7 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 plate. Shred using two forks, or leave the breasts whole according to preference.
06 - In a small bowl, stir together the cornstarch and cold water to create 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. Stir to coat evenly, cover, and cook on High for an additional 15-20 minutes until the sauce has thickened.
08 - Serve hot over cooked rice, quinoa, or steamed vegetables. Garnish with chopped fresh parsley or green onions.