01 - Whisk together the soy sauce, honey, hoisin sauce, rice vinegar, brown sugar, sesame oil, garlic, ginger, and red pepper flakes in a medium bowl until thoroughly combined.
02 - Arrange the chicken drumsticks in the slow cooker. Pour the prepared glaze over the chicken, turning each piece to ensure even coating.
03 - Cover and cook on low heat for 4 hours or until the chicken reaches an internal temperature of 165°F and is tender.
04 - Transfer the cooked drumsticks to a serving platter and cover loosely with aluminum foil to keep warm.
05 - Pour the cooking liquid into a small saucepan. Combine cornstarch and water in a small bowl to create a slurry, then stir it into the saucepan. Bring to a boil over medium-high heat, stirring constantly until thickened, approximately 2-3 minutes.
06 - Brush or spoon the thickened glaze generously over the drumsticks. Garnish with sliced scallions and sesame seeds before serving.