Preheat the oven to 400°F (200°C).
Scrub the potatoes under cold water, then pat them completely dry with a towel – this step ensures the skins crisp up beautifully.
Using a fork, pierce each potato 5–6 times to let steam escape while baking. Rub each one with olive oil or melted butter, then sprinkle generously with coarse salt.
Place the potatoes directly on the oven rack or on a baking sheet. Bake for 45–60 minutes, depending on size, until the skins are crisp and a fork slides in easily. For extra-crisp skins, bake an additional 10 minutes.
Slice each potato lengthwise and gently fluff the inside with a fork. Season with salt and pepper.
