Preheat the oven to 300 degrees Fahrenheit and line several baking sheets with parchment paper.
Scrub the beets well with a brush and cut off the tops.
Use a mandolin slicer to slice the beets thin (1/16”).
Place the beet slices in a large bowl, drizzle the oil and salt over the top, and toss well.
Let the beets sit in the oil and salt for 10-15 minutes, until they release their natural juices.
Toss the beets again and drain off the liquid. If some of the beets have a lot of oil coating them, pat them lightly with a paper towel, removing some of the oil.
Lay the slices out in a single layer on the prepared baking sheets.
Bake for 45-60 minutes until crisp, but not burnt. Test them after 45 minutes and bake longer if necessary.
Remove the beet chips from the oven and cool completely before eating. Add more salt to taste. Store leftovers in an airtight container.