Grease a large baking dish, then place the leg of lamb in it, skin-side up. Score the skin in a crisscross pattern.
Prepare a mixture of olive oil, Herbes de Provence, pepper, a bouquet garni, and garlic cloves that have been peeled and crushed.
Generously brush the leg of lamb with this mixture, turning it in the baking dish. Be sure to coat the slits thoroughly.
Bake for 15 minutes, then turn the leg of lamb over. Bake for another 15 minutes, then lower the oven temperature to 150°C (300°F) and continue baking for 3½ hours.
Baste the meat regularly with the juices from the bottom of the pan. Once cooked, serve with potatoes or flageolet beans.
