Heat a heavy pot filled with oil to 350 degrees. Using a mandolin, slice potatoes lengthwise into pieces less than 1/8 inch thick. Place potato slices on a surface covered in a paper towel to absorb dampness.
Chop sage and set aside. Assemble a large baking sheet covered in a paper towel to place fried chips. Once oil is at 350, drop potato slices in batches of 4-8 (depending on size of slices) into pot using a pair of metal tongs. After 30-60 seconds, flip once, and allow to cook til crisp, about 30 seconds more. Place on paper towel-lined baking sheet, sprinkle with salt. Repeat until all slices are fried.