Unwrap the thawed turkey, remove any plastic thermometer or drumstick holders. Rinse under cold water, and pat the bird as dry as possible. Lightly salt the entire bird with kosher salt, then place the turkey on a platter and refrigerate uncovered for 2 to 4 hours (or overnight) to help dry the skin.
Preheat the smoker to 325°F. Remove the turkey from the fridge and blot the turkey again to remove any remaining moisture. Stuff the cavity with the orange, onion, carrot, celery, rosemary, thyme, and sage. These ingredients will be discarded after cooking but add flavor as the turkey smokes.
Tie the legs together with butcher’s twine to hold the shape and close the cavity. Tuck the wings under the bird.
Mix all of the seasoning ingredients together, reserving one third. Rub the turkey with oil and season all over with two thirds of the blend.
Place the turkey on the smoker and close the lid. Let it smoke for 90 minutes to two hours.
Melt the butter in a small saucepan over medium heat. Whisk in the remaining seasoning.
Open the smoker and baste one side of the turkey with the seasoned butter. Rotate the bird 180° and baste the other side. Close the lid and let the turkey finish cooking.
Remove the turkey when the breast reaches 160°F and the thigh reaches 170°F. Let it rest (covered) for at least 20 to 30 minutes before carving.