Preheat oven to 375° F. For easy cleanup, line two large baking sheets with foil. Spray lightly with oil, then use a paper towel to spread it all over the bottom and remove any excess. Slice the potatoes crosswise, about 1/8-inch thick. Place on the baking sheets in one layer. Spray the tops lightly with the oil. Pat off any excess with a paper towel. Place in oven on two racks and bake, switching racks halfway through, until brown and crispy, about 30 minutes. (Some of the slices may brown more quickly than others. If that happens, just remove them and continue baking the others.) Gently remove the chips from the pans and place on paper towels. Add salt while still warm. Chips may be served immediately, or allowed to rest while making the remainder of the dinner. Leftovers, if there are any, stay crispy if wrapped loosely in foil and stored in the refrigerator. Bring them back to room temperature before serving.