Do you know for a four legs table no matter the floor it sits on. There is always a rotational position where all it's legs touch ground at the same level.

For circular tables that are uneven you can just rotate the table until it sits right.

For square tables you may check the 90° angles to see if you are lucky.

Edit: This theory works with even legs + uneven (bumpy) floors. For your own safety do not test this the other way around.

Why not just get some of these

A cool thing is, you can achieve the same effect by rotating the table in a circle (if possible) until you find a stable angle, since for 4 points on a circle there has to exist at least one rotation angle where they are on the same elevation.