Nathan Young wrote in
:

When filing en route, what do you use as the departure airport? I
always give the actual departure airport even though I left there some
time ago. For my route of flight, I just use the closest VORs
remaining on the flightplan.

There is no requirement that an IFR clearance start or end at an airport.
You can give any fix you like, preferably still ahead of you. It can be a
VOR, NDB, intersection, or just lat/lon. A named fix of one sort or another
makes it easier on everyone, though.

--
Regards,

Stan