How would non-aspected Austerities work, exactly? (Summoner-related)

[Exodus-E]

The way I understand it, in order for Summoners to actually summon an Egi, first they need to defeat a Primal in battle, THEN perform something called "Austerities of X" (X being a given aspect), which are pretty much rituals that allows them to call forth and tame the essence of said Primal (dubbed "Egi" in ancient Allag).

These "austerities" have to be done in places where their aspect is strong (for the ones we got so far, Sagolii Desert for Fire, North Shroud's wasteland for Earth and near the ruins of the Floating City of Nym for Wind).

Now, let's pretend that the Summoner job eventually gets an Egi out of all 6 aspects.
Then what?

How would non-aspected Primals work (if we get around getting their Egi in the future), exactly?
Where would their "austerities" take place?
Places with high concentration of aether? Or something else entirely?