Slice potatoes into 1/8-inch rounds for thicker potato chips. For thinner ones, use a mandolin to cut very thin slices. Toss slices in a medium bowl with oil and salt to coat evenly.
Coat a large microwave-proof plate with cooking spray. Arrange some potato slices in a single layer on the plate.
Microwave, uncovered, on high until some slices start to brown, 2 to 3 minutes (depending upon potato thickness and microwave power).
Turn slices over (they will be hot, so take care with your fingers) and continue microwaving until they start to crisp and brown around the edges, about 35 seconds for very thin potato slices to 2 to 4 minutes for thicker slices.
Check frequently and rearrange slices as needed to prevent scorching.
Transfer chips to another plate and allow to cool completely. (they will crisp up more as they cool.) repeat process with remaining slices.
Storage: store in an airtight container for up to 3 days.