Sprinkle the turkey inside and out with salt and pepper. Put the quartered onion and halved celery ribs inside the cavity of the turkey.
Place the turkey, breast side up, in a roasting pan. Cover the top of the turkey with slices of salt pork.
Place the turkey in the oven and bake about 30 minutes. Rotate the pan occasionally as the turkey bakes.
Scatter the whole celery ribs, carrot rounds, sliced onions, parsley, bay leaves, sage, and thyme around the turkey. Pour the stock around the turkey. Cover the roasting pan and continue cooking 1 hour.
Reduce the oven heat to 350 degrees. Continue cooking, basting often, about 1 hour more.