Heat oven to 200C/fan 180C/gas 6. Scrub the baking potatoes, then pat dry. Slice lengthways into three. Drizzle olive oil over a large baking sheet. Place the potatoes on the baking sheet, drizzle with olive oil, rub all over, then generously sprinkle with sea salt. Bake for 40-45 mins (longer for extra crispiness) turning halfway, until golden brown and tender.