Draw in a line which will be used to cut the base:
and snap it to the endpoint:
then select the entire line and offset it by one-half the endmill diameter which will be used for this cut:
If desired, extend the line and break it up so as to create tabs.
Delete everything which is not needed, export to PDF, convert to SVG, et voila!
(And then we get reminded that Carbide Create doesn’t do well importing lines…)