Check out https://en.wikipedia.org/wiki/ThreeBallot https://en.wikipedia.org/wiki/ThreeBallot It has some criticism, but IMO this is a very simple and effectiv

Check out https://en.wikipedia.org/wiki/ThreeBallot https://en.wikipedia.org/wiki/ThreeBallot It has some criticism, but IMO this is a very simple and effective method. And there are better ideas out there too. I think we can even build a mechanical machine (like out of buttons connected to stamps/ink) that can create valid threeballots. That way you don't have to explain the instructions.