Draft your design in InkScape. If there's any text, convert it to a path before or during exporting (Path → Object to Path).
Save as PDF (tested PDF v1.5).
pstoedit -f "dxf: -ctl -mm" shape.pdf shape.dxf
Install the tool using
sudo apt install pstoedit
or
yum install pstoedit
Tested with FreeCAD 0.16.
Use the "legacy Python importer" (check this under Preferences → Import-Export → DXF).
Tested with version 2.1.2.
Use File → Import → Block and select the DXF file.