Pulse the garlic, orange juice, Scotch bonnet, scallions, vegetable oil, brown sugar, cider vinegar, thyme, ginger, allspice, nutmeg and some salt and pepper in a food processor or blender until almost smooth.
Put the chicken in a large baking dish or resealable plastic bag and coat in the jerk marinade. Marinate in the refrigerator for least 3 hours and up to 6 hours.
Prepare a grill for indirect cooking.
Place the marinated chicken, skin-side down, over direct heat and cook until dark brown grill marks appear, about 3 minutes. Turn the chicken over and cook until grill marks appear on the reverse side, another 3 minutes.
Move the chicken to the indirect heat part of the grill and cook, skin-side up, until the skin is crisp and an instant-read thermometer inserted into the center of a thigh registers 160 degrees F, about 25 minutes.
Transfer the chicken to a platter and let rest for 5 minutes before serving.