Heat oven to 425 degrees. Cut 1/4-inch horizontal slits in potatoes, stopping before cutting through to keep potato intact. You can use two chopsticks on either side of potato as a guide to prevent cutting through. Rub potatoes all over with olive oil, and carefully brush between slits. Arrange potatoes, not touching, in a baking dish. Generously, season with salt and pepper. Bake for one hour, then remove and brush tops and sides with more olive oil. As necessary separate the slits to add olive oil. Bake for an additional 30 minutes until tender and edges are crispy. Serve immediately. Have extra olive oil and sea salt on hand for drizzling and sprinkling.