This print uses a couple pieces of 5/16-18 (or M8x1.5) threaded rod to connect the two parts together. Print two of them, in the orientation shown in the photo, no supports required. 

Before assembly, it may be helpful to ream out the insides of the threads by threading the rod into them and working it back and forth a few times. This will make assembly easier.

To assemble, thread both rods into one half of the stand, and keep going until the rod sticks out the other side to about the width of the stand. Then unthread each rod from the first half, while simultaneously threading it into the other half, so that they are threaded into both halves equally.