Turn a grill on high, place cast iron skillet on grates and allow to preheat with grill. Butterfly chicken, trim excess skin and fat, season generously with spice rub of choice. Add chicken to grill skin side up, set cast iron skillet on top of chicken and close the grill lid. Turn heat to low. Cook chicken until cooked through and juices run clear (My medium sized chicken took 15 minutes or so). Remove from grill and cut into pieces- it should be easy to do!