Coarse sea salt and freshly cracked black pepper to taste
Preheat the barbecue to medium-high. Meanwhile, with a sharp, narrow knife, make numerous, deep slits into the flesh of the lamb. Stuff the garlic slices into the slits. Brush the lamb with the olive oil; rub with the herbes de Provence, salt and pepper. Set the lamb on one side of the barbecue; close the lid. Turn the heat off on the side of the barbecue the lamb is sitting on; leave the other side set to medium-high. Cook the lamb, turning occasionally, until the desired doneness is achieved; 65 to 75 minutes should cook the lamb to medium, medium rare.