Remove the whole chicken from the packaging and remove any giblets. Save the giblets (and the back bone) for homemade chicken stock, if you’d like.
Cut off the excess fat that is often found at the bottom of the chicken, near the tail. Place the chicken breast down on a large cutting board. Now, all you need is kitchen shears to remove the backbone.
Using the kitchen shears, cut along the spine on one side, all along the backbone, and then on the other side of the backbone. Remove the backbone and flip the chicken breast side up.
Using the bottom part of the palm of your hand, put a lot of pressure in the center, right between the two breasts. Push down to flatten the breast plate until you hear small crack.
Seasoning the chicken:
Combine oil, lemon zest, and seasonings in a small bowl and mix it well.
Use your fingertips to very gently pull the skin away from the breast meat and add some rub over the breast meat.
Use about 2/3 of the rub for the top, skin side of the chicken, and about 1/3 of the rub for the underside. Make sure you do rub on both sides!
Prepare the grill:
Set a drip pan under the grill grate, underneath where you will be cooking the chicken.
Prepare the grill to have two temperature zones because you will be cooking the spatchcock chicken over indirect heat and then finish it over direct heat. You are looking for medium temperature of (375°-400°).
Grilling spatchcock chicken:
Insert the leave-in meat thermometer probe into the breast meat, into the thickest part, along the bone but not quite touching the bone.
Place chicken on the grill breast up and close the grill. Cook spatchcock chicken over indirect heat for 45-50 minutes, until it reaches 160°.
Open the grill and use long metal tongs to move the chicken over to the direct heat. Let it cook over direct heat for a couple of minutes on each side, until internal temperature gets to 165°.
Take chicken off the grill and let it rest on the cutting board for 5-10 minutes before serving.