01 - In a medium bowl, whisk together the soy sauce, honey, hoisin sauce, rice vinegar, brown sugar, sesame oil, garlic, ginger, and red pepper flakes (if using) until well combined.
02 - Place the chicken drumsticks in the slow cooker. Pour the glaze over the chicken, turning drumsticks to coat evenly.
03 - Cover and cook on low for 4 hours or until the chicken is cooked through and tender.
04 - Remove drumsticks to a platter and cover loosely with foil.
05 - Pour the cooking liquid into a small saucepan. In a small bowl, mix cornstarch and water to form a slurry. Stir the slurry into the cooking liquid.
06 - Bring the sauce to a boil over medium-high heat, stirring constantly until thickened, about 2-3 minutes.
07 - Brush or spoon the thickened glaze over the drumsticks. Garnish with sliced scallions and sesame seeds before serving.