In a large mixing bowl, whisk together the Korean gochujang paste, vegetable oil, oyster sauce, light soy sauce, white sugar, rice vinegar, mirin, sesame oil, grated garlic, and ginger until well combined. Carefully coat the whole chicken with the marinade, ensuring every nook and cranny is covered. For the best flavor, cover the bowl and let it marinate in the refrigerator for 8 to 16 hours.

Once the chicken has marinated, take it out of the fridge and allow it to sit at room temperature for about 30 minutes. Meanwhile, preheat your oven to 356°F (180°C).

Place the marinated chicken in a roasting pan, ensuring to leave space for air circulation around it. Bake uncovered in the preheated oven for 30 minutes until the skin starts to brown. After that, cover the chicken with aluminum foil and continue roasting for an additional hour or until the juices run clear when pierced with a knife.

After roasting, remove the chicken from the oven and let it rest for 15 to 20 minutes.

For those craving extra crispy skin, turn the oven to broil after resting. Brush the chicken with a tablespoon of the reserved, boiled marinade and broil for 1 to 2 minutes.