Rinse the roast under cold water, pat dry with paper towels, and place on a cutting board. Following the line of the bones, cut the meat away from the bones in 1 piece.
Season the meat and the bones all over with the salt and pepper. Rub the meat and bones all over with the garlic.
Fit the meat back onto the bones, making sure to match the meat and bones up where they were cut apart, and tie together between each bone with butcher’s twine.
Place the roast on a large plate and refrigerate uncovered overnight.
Remove the roast from the refrigerator and let it sit at room temperature for 30 minutes to 1 hour. Meanwhile, heat the oven to 200°F and arrange a rack in the lower third.
Place the roast fat-side up (the bones will be on the bottom) on a roasting rack set in a roasting pan.
Roast until the center reaches 120°F on an instant-read thermometer, about 4 to 6 hours.
To Finish the Roast:
Place the roasting pan on a wire rack, tent the roast loosely with foil, and set aside in a warm place for at least 30 minutes or up to 1 hour. Meanwhile, increase the oven temperature to 450°F and keep the rack in the lower third.
When the roast is done resting, remove the foil and crumple it into a ball. Place the ball of foil under the bones of the roast to prop up the less exposed area of fat.
Roast until a dark brown crust forms over the entire top surface, about 8 to 10 minutes. Remove the roast to a cutting board. Cut, remove, and discard the twine. Slice and serve immediately with au jus.