These went over so well nobody could wait for them to cool.
1 tablespoon olive oil
Peel the beets and slice them really thin, about a 1/16 of an inch. I couldn't get them as thin as I would have like so I either need to invest in a mandolin or dig out the food processor. I was too lazy to clean the food processor so I used a knife.
Put them in a bowl, drizzle the olive oil and toss until they are lightly covered. It was surprising how far that oil went.
Spread them on two pans and heat the oven to 350 degrees. Put one pan on the rack on the top third of the oven and the other pan on a rack on the bottom third of the oven. Let them bake for 20 minutes until the edges start to look crisp and switch the pans around for another 20 minutes of baking. If they are still quite moist put them in again until they look crisp. Beware that they will crisp up a bit during cooling, unless they are eaten before they get the chance.