1. Cut potatoes crosswise into even 1/8-inch-thick slices; discard ends. Cut only as many slices as will fit in 1 layer in microwave; reserve remaining potatoes. Place slices in a large bowl and toss with oil and salt.
2. Line bottom of microwave with parchment paper. Arrange slices in a single layer on parchment, without overlapping, leaving space between slices. Microwave, uncovered, on high until slices have softened and curled on edges, about 3 minutes. Carefully turn each slice over and microwave on high until it starts to brown, about 2 minutes. (Watch carefully as slices can burn easily. Rearrange slices as needed to crisp evenly.) Transfer finished chips to a plate to cool completely. Place others back in microwave and cook in 30-second increments until all chips are done. (Time will depend on thickness of slices and power of microwave.) Chips will crisp more as they cool. Continue with remaining potatoes. Season with additional salt, if desired.