Note DC is the DC to find a hidden location by searching the hex

E.g. #3

E.g. #2

E.g.

Then, key each hex with departures from the default. Make liberal use of landmark/hidden/secret modifiers. To the extent applicable, use keywords to introduce key issues like Settlements, Creatures, Treasure, Trade Opportunities, etc. I use specific glyphs on the hexmap to mark keyed hexes...

I think you first need to define what is outside the hex key. For example, the default random encounter table, weather and basic description of the terrain (based on terrain type)....