2. Place the chicken breast side down on a cutting board. Using poultry shears, cut down along one side of the backbone, and then the other; discard the bone. Turn the chicken breast side up, open it out, and press down rmly with your palms to atten it. Place it in the freezer bag, seal, and ip several times to coat. Lay the bag in a shallow dish and marinate in the fridge for at least several hours, or, preferably, overnight, turning a few more times. 3. Heat a gas or charcoal grill to medium. Remove the chicken from the bag, reserving the marinade, and let it sit out for 30 minutes. 4. Baste the bird all over with the marinade, season with sea salt, and place it breast side down on the grill. Grill until the skin is a deep brown and shows grill marks, 12 to 15 minutes. Flip, baste, and grill for about 15 minutes more. The chicken is cooked when the juices run clear if the thigh is pierced or when an instant-read thermometer inserted in the thickest part of the breast reads 165째F. Just before serving, brush the chicken with fresh piri-piri sauce for an extra kick of heat.