Prepare a grill fire to 350° using pecan or hickory for smoke flavor.
Brush 3 tablespoons olive oil over both sides of the chicken and season with kosher salt and fresh ground pepper.
For the sauce: In a bowl, mix 1/2 cup olive oil with brown sugar, rice vinegar, soy sauce, sesame oil, garlic, ginger and chili flakes.
Place in a saucepan, cooking over medium heat. Bring the mixture to a boil, whisking often until sauce is thickened, about 3- 5 minutes.
Remove from heat. Pour ½ cup into a bowl for glazing the chicken and reserve remaining sauce for serving.
Cook chicken over indirect grill fire with the lid closed for 6- 8 minutes.
Turn the chicken and glaze with sauce in a thick coating. Close the grill and continue to cook another 4 minutes. Turn the chicken again, brushing with sauce.
Close the grill and cook another 2-3 minutes or until chicken reaches 165° using a digital meat thermometer.
Remove from grill and rest 5 minutes before serving.
Garnish with sesame seeds and chopped cilantro if desired. Serving with additional sauce drizzled over the chicken if desired.