Preheat the oven to 400 degrees.  Line a sheet tray with foil. Prick the sweet potatoes 3-4 times each, with the tines of a fork. Place in a single layer on the sheet tray. Brush all over with the oil and sprinkle all over with salt. Bake for 45-60 minutes, until the skin is crispy and browned and the tip of a paring knife slips easily into one of the potatoes. Let cool 5 min, then split open and top with all of your favorite potato toppings