Preheat the oven to 450 degrees F. Combine the soy sauce, oil, minced garlic, and lemon juice in a large mixing bowl. Add salt, pepper, and pepper flakes. Roll the chicken legs in the mixing bowl to coat them. Marinate these in the refrigerator for 30 minutes (optional). I did not marinade mine today. Place the chicken legs on a greased foil-lined large baking pan (9 by 13-inches). Bake for 30-40 minutes (turn the legs halfway through cooking) or until your meat thermometer registers 165 degrees in the thickest part of the leg. Let the chicken legs rest 5 minutes before serving.