Preheat the waterbath to 53.5°C.
Put the meat in a sous-vide bag, add olive oil, garlic cloves, thyme and pepper. Put the bag in the waterbath and leave it there for four hours. It will be perfect on the inside. Not on the outside. Not yet.
Make sure the barbecue is very, very, very hot.
Take out the meat, and pat it dry: we want to roast it, not cook it. Put it on the barbecue. It may catch fire, which is fine. Burn a good crust on all sides.
Cut the meat — how do you say it — against the fibers. Add salt. Enjoy.