While grill is heating, pound chicken breasts flat: sandwich between layers of plastic wrap, then pound to an even thickness of ¾ inch using a rolling pin.
Stir together spice blend.
Brush chicken breasts with olive oil, then sprinkle generously with the spice blend.
Carefully grease the grill with spray oil (you can also brush the grill with olive oil), then place the chicken on the greased grill.
Cook chicken for 2 minutes per side, then reduce grill heat to medium (roughly 450°F).
Continue cooking chicken until it reaches an internal temperature of 155°F. Remove chicken from the grill and cover with a bowl or baking dish. Allow to rest for 5 minutes. Chicken will continue to cook while it rests.
Slice chicken against the grain, and serve.
This grilled chicken is best served fresh, but leftovers can be kept for up to 4 days in the fridge.