Preheat the oven to 300ºF and line 2 baking sheets with parchment paper.
Use a mandoline slicer to cut the potatoes into paper-thin slices. You want them to be almost-transparent, but not quite. The thinner they are, the faster they will cook, and the crispier they will be.
Arrange the potato slices in a single layer on both baking sheets, without much overlap. Brush both sides of each potato slice with oil, then sprinkle with sea salt.
Bake at 300ºF for 15 minutes, then flip the chips over and bake for another 10 minutes. Be sure to watch the oven closely if your chip slices are particularly small, as they will cook the fastest. You want the chips to be lightly golden all over to get the crispiest results.
Remove any small chips that are looking browned at the 25-minute mark, then continue to bake for 5 more minutes. If the chips aren't all uniformly golden at the 30-minute mark, continue to bake them in 5-minute intervals until they are done, removing any brown pieces as you go, so they won't burn.
Let the chips cool on the pan for at least 5 minutes. They will crisp up even more as they cool. Serve right away with your favorite dip, or as a side dish.
Homemade chips don't store particularly well. They will get a little softer if you store them in the fridge overnight, but you can re-heat them in the oven again, if you want to crisp them up the next day.
For air fryer or dehydrator methods, be sure to check out the additional tips in this post below!