Preheat the oven to 190 degrees C. Warm a roasting tin or oven-proof casserole dish while you are preparing the potatoes.
Place peeled potatoes in a saucepan and cover with cold water. Bring to the boil and simmer for 10 minutes then drain really well in a colander, shaking them for a few seconds to fluff them up at the edges.
Carefully arrange the potatoes in the roasting tin and baste them with hot oil. Sprinkle over some sea salt and roast for an hour, turning them every 20 minutes or so, until they've crisped up and are golden all over.
Make sure the potatoes are really dry after par-boiling them for 10 minutes. This will prevent them from sticking to the tin as they roast.