Preheat the oven to 300°F and line two baking sheets with parchment paper.
In a large bowl, toss the sweet potato slices with 1 tablespoon of oil and 1/4 teaspoon of sea salt. Make sure each slice is evenly coated.
Arrange the slices in a single layer on one of the prepared baking sheets.
Repeat the process with the beet slices and arrange them on the second baking sheet.
Bake the sweet potato chips for 15 minutes, then rotate the pan and bake for an additional 15 minutes. Check often and remove any chips that turn golden or crispy early.
For the beet chips, let them rest for 10 minutes after coating to draw out excess water. Then bake for 15 minutes, rotate, and bake for another 30 minutes, rotating every 15 minutes to ensure even cooking.
If any chips are still slightly moist, return them to the oven for an extra 5–15 minutes, checking frequently to avoid burning.
Allow the chips to cool completely before storing them in an airtight container.