The thing itself isn't really interesting, it's just an example of a 3d-printed solder stencil. It was created using https://solder-stencil.me, which uses pcb-tools and OpenSCAD to generate STL files from Gerber files.

The app makes creating stencil as simple as uploading two files, but you can also find the underlying code at https://github.com/kirberich/gerber_to_scad and run it yourself.