Place racks in top and bottom thirds of oven; preheat to 400ºF. Slice potatoes 1/8-inch thick. In a bowl, toss potatoes with oil until coated.
Mist 2 large baking sheets with cooking spray. Place as many potato slices as you can fit in a single layer on sheets. Bake until golden brown, switching baking sheets from top to bottom and front to back twice, 18 to 20 minutes total.
Immediately sprinkle chips with salt and cool on wire racks. Repeat with remaining potato slices.