Halve the lemons lenghtwise and slice into paper-thin half-moons, about an 1/8-inch-thick or thinner. Discard any seeds. Stack the slices and cut into thirds.
In a medium bowl, combine the lemons, half of the mint, the peperoncino, and the olive oil. Season with salt and toss well. Set aside to marinate for at least 1 hour. Serve garnished with the remaining mint.