I happen to see a video on youtube on how to make an holographic projector from a cd case (credits to American Haker for it https://www.youtube.com/watch?v=9t0cOYvOy4M).

Well I have to try.....cutted the cd cases (not very well) added tape and tried to glue but......the pyramid was not too straight an difficult to balance on the phone.

So I said....let's make a base. And that's it.

Cut 4 trapezoid from the cd case:
small base: 1cm
big base: 6 cm
height: 3,5 cm

Print the base (mine was at 0.2 layers height).
Then plug the small bases in the printed base.
Find some holo video on youtube....and enjoy