Heat oven to 350 degrees and position racks in top and bottom thirds. Wash potato (or potatoes) thoroughly with a stiff bristled brush and cold water. (Keep a separate vegetable brush in the drawer for scrubbing potatoes.) Don’t scrub the skin off, just clean it. Dry well, then using a fork poke 8 to 12 deep holes all over the potato. Place in a bowl and coat lightly with oil. Sprinkle with kosher salt and place potato directly on the rack in the middle of oven. Place a baking sheet on the lower rack to catch any drippings.
Bake 1 hour or until skin feels crisp but flesh beneath feels soft. Serve by creating a dotted line from end to end with your fork, then crack the potato open by pushing the ends towards one another. The potato will be hot and steamy so be careful! If cooking more than 4 potatoes, extend cooking time up to 15 minutes. Add sprinkled cheese to melt over the hot potato, sour cream, green onions, etc.