1. Preheat oven to 200 degrees F. Line 2 large baking sheets with parchment paper.
2. Toss beet slices with oil and salt. Spread in a single layer on the prepared baking sheets.
3. Bake on the upper and lower oven racks until crisp, rotating the pans top to bottom and front to back halfway through, about 3 hours. Cool on the pans for 30 minutes before serving.