In a bowl, whisk together all sauce ingredients until smooth.
Add half of the sauce to the chicken and toss to coat evenly.
Transfer chicken to the slow cooker.
Add a small splash of broth or water to keep the chicken moist.
Cook on LOW for 4–5 hours, until chicken is tender.
Add the remaining sauce, stir, and let warm through for 5–10 minutes.
Finish with sesame seeds, black pepper, and chili flakes if desired.
