Preheat oven to 425*F. Remove organ pack and neck from inside chicken. DO NOT RINSE CHICKEN! Pat outside of chicken dry. Sprinkle 1T salt and 1 T of lemon pepper into body cavity. Tightly pack the body cavity with lemon, onion, celery and fresh thyme. Using kitchen twine, tie legs tightly together to enclose the cavity of the bird. Place the bird in grill pan. Tuck wings underneath. Drizzle bird with olive oil, ensuring the whole bird is coated. Generously sprinkle remaining salt and lemon pepper over outside of bird. Insert oven-safe meat thermometer into bird between the breast and leg (roughly the groin area). Set thermometer to 165* finished temperature and turn thermometer on. Place bird in oven and roast until thermometer sounds at 165*. When bird is done, remove from oven and let rest 10 minutes before slicing.