Made in DiamondAge PLA on an Ultimaker 1.
The two parts of the stand are connected via three tapered 270 degree collars which are jam fits into corresponding slots in the right hand and left hand uprights.
This allows the stand to be opened the desired amount and then locked in that position.
This works well in PLA. I don't know how well it would work in ABS.
The leftmost stand in the photo is the as-drawn size. The other a 50% scale up in Cura.
Note that two locking wedge stl files have been posted. One is 50% of a full round and the other 75%.

Obviously the side plates should be printed lying down. Note that one of the vertical edges is radiused so should be away from the print plate.
The locking wedge should be printed the wider side down.

To assemble the stand hold the two plates flat against each other. Insert the three locking wedges at the top of the slots in the plates. Open the plates the desired amount. Centralise the wedges horizontally and the then press down firmly to lock into position.