In a saucepan on a stove, combine sesame oil and cornstarch and heat until bubbling.
Reduce heat and add garlic, rice vinegar, ginger, soy sauce, honey, Korean chili paste, and brown sugar. Heat for 5 minutes.
Add scallions, sesame seeds, and red pepper flakes, and cook until simmering. Remove from heat and let cool.
Marinate chicken legs in the prepared sauce for at least 6 hours.
Preheat the grill, grill the chicken legs for 25-30 minutes, basting with reserved marinade, and cook until done.
Let the chicken rest before serving, garnish with sesame seeds and scallion tops.
