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.
To Season Chicken:
Combine all the seasonings in a small bowl and mix well. Combine a teaspoon or so of seasoning mix with softened butter and mix that well.
Gently separate the skin away from the breast meat by running your hand underneath the skin. Add some butter between the skin and the breast meat and spread it around as evenly as you can.
Rub the whole chicken with oil over the skin and underneath. Sprinkle about 1/3 of the seasoning mix all over the bottom of the chicken, pat it on, and flip. Sprinkle about 2/3 of the seasoning mix all over the top, in even layer. Don’t rub but pat it on.
Smoking The Chicken:
Set a drip pan under the grill grate if needed and prepare the smoker to 225°. Depending on the smoker, try to maintain temperature between 225° and 250°.
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 smoker grate breast up and close the lid. Smoke chicken for 3 to 4 hours, depending on the size. Make sure to track the temperature. Internal temperature of the chicken should be 165°.
Take chicken off the smoker and let it rest on the cutting board for 5-10 minutes before serving.