01 - Whisk together soy sauce, honey, hoisin sauce, rice vinegar, brown sugar, sesame oil, minced garlic, grated ginger, and red pepper flakes in a medium bowl until fully combined and smooth.
02 - Arrange chicken drumsticks in the slow cooker insert. Pour the prepared glaze over the chicken, turning each piece to ensure even coating on all sides.
03 - Cover and cook on low heat setting for 4 hours until chicken reaches internal temperature of 165°F and meat is tender enough to pull easily from the bone.
04 - Transfer cooked drumsticks to a serving platter using tongs. Cover loosely with aluminum foil to maintain temperature while preparing the sauce.
05 - Whisk cornstarch and cold water in a small bowl until completely dissolved and no lumps remain.
06 - Pour cooking liquid from slow cooker into a small saucepan. Bring to boil over medium-high heat, stir in cornstarch slurry, and cook while constantly stirring for 2-3 minutes until sauce reaches desired consistency.
07 - Brush or spoon thickened sauce generously over each drumstick, ensuring all pieces are evenly coated with the glossy glaze.
08 - Sprinkle thinly sliced scallions and sesame seeds over the glazed drumsticks just before serving.