You can demonstrate this very easily with your phone (all directions given assuming the phone is facing you, oriented vertically): rotating it cw/ccw will be st

You can demonstrate this very easily with your phone (all directions given assuming the phone is facing you, oriented vertically): rotating it cw/ccw will be stable (you're on the shortest axis, only the depth of your phone, probably a few mm), flipping it left-to-right will be stable (you're on the longest axis, the height of your phone, probably ~5"), but flipping it top-to-bottom will result in an uncontrollable spin, as that's the middle axis (the width of your phone , probably 2-3")