I happen to know FreeCAD for designing 3d objects and was struggling with creating my board cut in KiCad.I followed the following steps. I am leaving this mainly as a note to self but others might find it useful.
Start FreeCAD
File → New
In the dropdown select the Part design
Create Body
Create Sketch
Select XY plane (and OK)
Now draw your design use lines and contraints(if possible create a fully contrained drawing)
Close and now Create a pad (e.g. extrude the pice)
Switch the tab from Tasks to Model
Click on PAD
Use file export → dxf to export the (2d) representation of the part in dxf format)
KiCad:
Start Kicad
Create new project
Click the new footprint editor
Goto preferences → Manage foorpring libraries
Click Project specific
Click the “file/directory icon” and select the current project directory(this is a bit confusing but just do it)
File - new footprint
File - Import → Footprint outlines from dxf and select the file
Save and select the project library (e.g. if your project is called demo select the demo library)
In your shematics assosiate a component with this footprint or in the pcb editor perss “O” and select your compoments.
Here is a video (7 minutes) of creating / importing the footprint)
