In a bowl, whisk together soy sauce, honey, rice vinegar, sesame oil, garlic, ginger, and red pepper flakes.
Add the chicken pieces to the marinade, mix well, and let marinate for at least 30 minutes (or overnight for best flavor).
Thread the marinated chicken onto soaked wooden skewers.
Preheat the grill to medium-high heat and lightly oil the grates.
Grill the skewers for about 10-12 minutes, turning occasionally, until the chicken is fully cooked.
In a small saucepan, heat the remaining marinade and bring it to a simmer.
Stir in the cornstarch mixture and cook until the sauce thickens.
Brush the grilled skewers with the teriyaki sauce before serving.
Garnish with sesame seeds and green onions, then serve immediately.