Well, how you should proceed depends on your printer. When I designed this, I was using a higher end 3D printer which uses a soluble support material, which is dissolved after the print is done. That way having overhangs isn't a problem.
However, most hobby printers don't have that option. To get around that, if you were so inclined, your best option would be to modify the models and add some support columns underneath. How many you need and what width will depend on your specific printer. Ideally you'll want to design them so that they can be snapped off easily.
I hope that was of some help! Sorry the design isn't more hobby printer friendly, when I originally made it I was just intending it for my own personal use, then just kind of posted it here on a whim. Good luck!