Combine the orange marmalade, rice wine vinegar, dark brown sugar, soy sauce, sesame oil and red chili flakes in a small saucepan and bring to a simmer to melt the marmalade. Simmer for a few minutes to thicken the glaze and then turn off the heat and set the glaze aside.
Baste the chicken with some of the glaze. (This is where you have to pay attention to not letting the chicken get too dark.) Flip the chicken over to breast-side up and baste again. Grill on medium-low heat for 20 more minutes, or until the temperature reaches 165°F with an instant read thermometer inserted into the thickest part of the chicken breast and thigh. Brush the top with glaze once again and flip the chicken over to crisp the skin for 5 minutes or so before removing it from the grill.