Closing is a process where you overtly state your intent and work through the conditions for that end-state to exist.
Closing need not be a long drawn out process. You can close after an initial meeting, or you can wait for a few meetings before you do so.
The more important thing is to know what X threshold of interactions you want to have before you close. Why? Because no number of X interactions will give you 100% comfort that you can close comfortably. The very nature of closing is an uncomfortable one, and the likelihood of X+1 interaction being significantly more comfortable is very unlikely.
Instead, the premium should be on timing and momentum, and thus closing at X or even X-1 interaction is good to optimize for early timing and momentum.
For me X is oftentimes 3 because I discard the initial 2 contact points. I find that the first 2 contacts contain high variance on revealing a person's character, and contact point 3 onwards really only show a person's true self.
For the theory on when to close, see the theory behind [optimal stopping theory] (https://en.m.wikipedia.org/wiki/Optimal_stopping?wprov=sfla1).
Another question is how to remove the conditions to close. One of my favorite techniques is to exactly play this question back to the person, ie.
if your conditions can be met, can I count on your commitment into this close?
This technique front-loads the main issue so that commitment is apparent, and the conditions can worked on, not the other way around.
What I have found over time is that the above conversation is still best done face to face either live or virtually. There are too many human emotional factors involved that it is best to be able to read it all.