Prep the chicken. Trim excess fat and pat the chicken dry.
This helps it sear better if you choose to brown it first and keeps the sauce from getting greasy.
Make the sauce. In a bowl, whisk together honey, soy sauce, minced garlic, ketchup, rice vinegar, sesame oil, black pepper, red pepper flakes (if using), and chicken broth.
Optional: Brown the chicken. Heat a splash of oil in a skillet over medium-high. Sear the chicken 1–2 minutes per side. This step adds flavor but isn’t required.
Load the slow cooker. Place the chicken in the slow cooker.
Pour the sauce over the top, turning the pieces to coat.
Cook low and slow. Cover and cook on Low for 3.5–4.5 hours (thighs) or 2.5–3.5 hours (breasts), until the chicken is tender and reaches 165°F/74°C. Avoid overcooking, especially with breasts.
Thicken the sauce. Transfer the chicken to a plate. Stir the cornstarch slurry into the sauce.
Cover and cook on High for 10–15 minutes, or simmer in a saucepan until glossy and slightly thickened.
Shred or slice. Shred the chicken with two forks or slice it. Return it to the slow cooker and toss with the sauce.
Finish and serve. Taste and adjust salt, pepper, or heat. Serve over rice or noodles and top with sesame seeds and green onions.