Add the kosher salt, thyme and rosemary to a mortal & pestle and crush into a powder. Add the paprika, pepper, onion powder and garlic powder and mixed to combine.
Remove the neck, giblets, and liver from the cavity of the turkey and reserve neck for gravy. Pat the turkey dry with paper towels inside and out. Season well inside and out with the dry rub, ensuring to get into all the creases and crevices.
Place the turkey on a rack over a sheet pan and refrigerate for at least an hour, up to 12 hours.
Preheat the convection oven to 390°F (or conventional oven to 415°F)
Stuff the turkey with the garlic, celery, rosemary & thyme. Loosely tie the drumsticks together with kitchen string and fold the wings underneath the bird. Place the turkey on a flat rack over a shallow roasting pan and cooked for 20 minutes. Remove from oven and brush all over (including underneath) with olive oil. Rotate the pan 180°, return to oven and cook for 20 minutes.
Lower the temperature to convection oven to 300°F (or conventional oven to 325°F), baste with ⅓ cup broth. Roast the turkey, uncovered (basting every 30 minutes) until an instant-read meat thermometer registers 165°F when inserted into the largest section of thigh (avoiding the bone), about 2 ¾ to 3 hours total cooking time.
If skin starts to brown too much, place tinfoil over darkest spots leaving lighter areas uncovered. Remove from the oven and place on a platter. Tent with aluminum foil and let rest for 20 minutes before carving.