Coat the thinly sliced beets with oil of choice (about 2-3 tablespoons, depending on the amount of beets used). This can be done by tossing them in a bowl (**be sure to coat each beet entirely) or lay them out on a parchment lined rimmed baking sheet, lightly coating each side with a pastry brush or with your hands. (warning: it's going to be a little messy as beets have a lot of juice)
Once the oiled beets are evenly placed on your rimmed baking sheet, use another matching rimmed baking sheet (with the bottom lightly oiled) and place it on top of the beets. This creates a type of "press", helping the beets to cook evenly and flat. You can do two sets of these at a time if you have 4 matching rimmed baking sheets. You will need to rotate the sheets part way through the cooking process.
Bake the beets in the 'press' on the center rack of the oven, for 15-20 min (depending on the thickness of the beets). Check the beets a few times during the cooking process. When the edges of the beets start to dry out some, remove the top baking sheet.
Continue baking the chips uncovered for another 10-15 min or until they start to turn lighter in color and brown slightly. Remove the chips as they look finished. Watch them carefully at this point because they will burn quickly. Remove some of the smaller beets that cooked faster than the larger ones.
Allow to cool. Sprinkle with salt or any powdered spices you want to try. Chips should become crisp as they cool.