Make the sauce: In a bowl, whisk honey, soy sauce, ketchup, garlic, ginger, rice vinegar, sesame oil, red pepper flakes, and chicken broth until smooth.
Season the chicken: Lightly season the chicken with salt and pepper. Place it in the slow cooker in an even layer.
Pour and set: Pour the sauce over the chicken. Cover and cook on Low for 4–5 hours or High for 2.5–3 hours, until the chicken is tender and cooked through.
Thicken the sauce: Transfer the chicken to a plate.
Whisk the cornstarch and water, then stir the slurry into the sauce in the slow cooker. Cover and cook on High for 10–15 minutes, or until the sauce becomes glossy and slightly thick.
Shred or slice: Shred the chicken with two forks or slice it into chunks. Return it to the slow cooker and toss with the sauce.
Taste and adjust: Add more soy sauce for salt, a splash of vinegar for brightness, or a drizzle of honey for sweetness as needed.
Serve: Spoon the chicken and sauce over rice, quinoa, or noodles.
Garnish with sesame seeds and green onions.