Flower Light Fixture Lens Cover for Overhead Lights

I got flower stl file from http://www.thingiverse.com/thing:1227912.
I remix flower with Parametric Light Fixture Lens Cover for Overhead Lights.
from this VDO https://www.youtube.com/watch?v=avVNfIswkMU

in PART section
- import both stl files in FreeCAD software
- create shape from mesh for both of them
- advanced utilities to create shape to make both of them solid
- move flower to be on top of lens
- select lens and them flower
- click make a cut of two shapes
- save