How to check which side of a (cube) object touches the ground?

I am trying to make a rectangle box roll/tumble forward and sideways over it’s edges.
(I followed this great tutorial: http://cybereality.com/tutorial-how-to-make-a-cube-roll-on-a-grid-in-unreal-engine-4/)

BUT since I’m not working on a cube; not all sides are equally sized, so after each turn my pivot needs to be replaced.

I was wondering if there’s a way to indicate which side of my box is touching the ground so I could direct my pivot in the right place?