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 until fully incorporated and smooth.
02 - Arrange chicken drumsticks in the slow cooker. Pour the prepared glaze over the chicken, using tongs to turn each piece and ensure even coating on all sides.
03 - Cover and cook on low heat for 4 hours until chicken reaches internal temperature of 165°F and meat is tender enough to pull easily from the bone.
04 - Transfer drumsticks to a serving platter using tongs and cover loosely with aluminum foil to retain heat while preparing the sauce.
05 - Pour cooking liquid from slow cooker into a small saucepan. Combine cornstarch and water in a separate bowl to create slurry, then stir into the saucepan.
06 - Bring sauce to boil over medium-high heat, stirring continuously for 2-3 minutes until mixture thickens to coating consistency. Remove from heat.
07 - Brush or spoon thickened glaze generously over drumsticks. Sprinkle with sliced scallions and sesame seeds immediately before serving.