Preheat the oven to 120°C (approximately 250°F). Line two baking sheets with parchment paper.
Rinse and peel the beets. Thinly slice the beets with a knife or on a mandoline. Lay the slices on the baking sheets (the slices shouldn't touch). Season the beets lightly with salt. Add the beets to the oven and bake for 50 minutes, until crispy. Remove from the oven, let cool, and store in an airtight container.