1. You need hot coals, so light the fire in the meantime. Using a sharp knife, cut the potatoes into thin slices without cutting all the way through to the bottom. Tip Place each potato between the handles of two wooden spoons, then cut down to the handles of the spoons.
2. Rub the potatoes carefully all over with the olive oil, and season with the salt, sage and bay leaves or rosemary sprigs. I like to push whole pieces of herbs into the grooves here and there, but you can also chop them up and rub them on if you prefer. Garlic tends to burn if added now, so I only add it later.