Preheat the oven to 425°F. Prepare a baking pan by lining with foil and set aside. Place a potato on a cutting board. Arrange chopsticks on either side of the potato as a guide; this will help keep you from slicing all the way through the potato.
Using a sharp paring knife, make thin, vertical slices into the potato, making sure to stop before reaching the bottom. Make cuts anywhere from ¼ to ⅛ inch thick. Repeat with all potatoes.
Gently rinse each potato under cold running water, removing the starchy liquid from between the slices, then pat dry.
Place the potatoes on a microwave-safe plate and cover with a damp paper towel. Cook on high for 4-5 minutes, just until the potatoes are slightly softened.
Place the par-cooked potatoes on the prepared baking pan and brush each with olive oil or melted butter. Season each with about ¼ teaspoon of sea salt.
Bake for 30-40 minutes depending on the thickness of the potato, brushing with remaining butter half way through the bake time. Insert the tip of a knife a thick part of each potato to test for doneness; they should be tender in the center, but crisp & browned on the slices.