This design was inspired by Thing 13430, which it strongly resembles. However, it differs in that this was redesigned from scratch using OpenSCAD. We lower the center of mass of the paper being held; also, the slot holds the paper up more firmly without tipping over. This design is surprisingly stable despite not having any weights inserted into the base.
Our prints were made using 0.25mm extrusion of PLA with 2 walls and about 5% fill on a MakerGear M2. There were no difficult-to-print areas. Even a 0% fill probably could be used to produce front and back chambers suitable for filling with a weighting material (e.g., sand) after printing.
UK's colors are blue and white, so when printing the UK version either of those colors is preferable -- and the UK logo itself easily can be painted the other color. For example, the unit shown here is blue PLA with white paint applied to the surface of "UK". The texture of the extruded PLA allows most paints to grip well enough.