The other things, if you want to specify a non-ICAO airfield, is to use
1. a nearby airways intersection
2. the VOR-relative specification XXXRRRDDD e.g. MID270015 being 270 radial from MID, 15nm.
3. lat/long
It's no rocket science.
Especially as people flying from farm strips are on the whole less likely to fly in precise straight lines
Time to duck ....