There is now a file called "Base_for_Robo_3D_R1.stl" that you can download. It has a curvature similar to the top part of the Robo 3D 3D printer. At the bottom you can see three holes into which you can insert M3 screws to fix the base to the printer.
Please note that you will need to use support structures while printing and then break them of. Hope it works and that you like it. :)