Place oven rack in lower third of oven and preheat oven to 225°F.
If bones have not been pre-cut, cut along the bones from the thin tail end towards the thicker meaty end of the roast until about ½ inch from the end, leaving them attached but allowing you to fold the meat back to access the underside of the meat.
Combine minced garlic, salt, pepper, and chopped herbs in a small bowl and stir well.
Rub garlic and herb mixture on all sides of the meat, including the underside that you previously removed from the bones.
Fold the meat over to expose the bones and dd half of the rosemary and thyme sprigs to the top side of the bones, then fold the meat back over, so that the herbs are in between. Set the remaining herb sprigs on the top, fatty side of the meat, then tie the meat and bones together tightly with butcher's twine.
Place meat on a rack in a roasting pan. Add aromatics such as sliced onion and herbs if desired, and place in oven. If drippings begin to burn, add around ½ cup of water to the roasting pan, but avoid adding too much water so you don't steam the meat.
Cook until internal temperature reaches 120°F, for medium rare. See post for temp guide. Remove roast from oven and tent with foil. Allow to rest for 30 minutes, up to 1 hour.
Heat oven to 500°F and return roast to the oven for 10 minutes, until well browned.
Remove twine and herbs sprigs then cut bones from the roast and slice to serve.