The motor needs a place to be mounted and the wheel ideally would be supported on both sides of the axle…. but with a little tweaking it’s perfectly possible to use the same flat base part as the internal support (the wooden part in the picture). Depending on materials it might not be strong enough ‘as is’ but it should be fairly easy to add some simple steel support rods inside.
This is very cool, we went from 5 different parts that would need to be bolted together (making them still very large for storage, 72 parts in total) to 27 identical components… plus some simple (and cheap) connecting rods. It can also (hopefully) be set up in a few minutes and would lay flat under a bed. Nice.