How to print "holograms" inside "glass"

See more details and a video of the effect in my reddit post.

Disclaimer: yes, I know this aren't actually holograms =)

Instructions below are based on OrcaSlicer, I haven't tried this in other slicers.

Necessary modifications to the original “how to print glass” method:

1. take the model you want to make into a “hologram” and add it to the slicer
2. add a primitive (cube, cylinder, disk) to the buildplate, scale it to be bigger than the model
3. select both object and click “assemble”
4. now move the original object (that is now a part of the assembly) to the center of the primitive - as it is now part of the assembly it won't snap to buildplate
5. right-click on the object and select “change type” - “negative part”
6. (optional) go to “Strength” and set wall loops to 1
7. IMPORTANT go to “Strength” - “Advanced” and uncheck “Detect narrow internal solid infill”

For tests you can skip first 4 steps by using my STL - it's a cube with a cone inside.

After printing my quick and risky method of making all sides clear is:

• lightly sand all the walls so that layer lines aren't as protruding
• use a blowtorch (or a torch-like lighter) to quickly melt the outer layer. Be careful not to burn the plastic! 

100% sure that proper sanding+polishing or UV-resin coating will give better results and be less risky, but I haven't tried it yet cause I hate sanding and don't have any UV resin =)