The included Zip File contains an .STL that will allow you to 3D Print each of the pieces as one print.  
 
This is a rolling tray design in 6 parts that prints as one so that the two sides of the tray are able to fold over onto one another into a stash box. Push the balls through to one side to lock it in place; then push them back to center to open the box again.
 
The balls should be completely free floating in the sockets, allowing them to turn easily.