When I first tried the event on my own I was really disappointed that, like several things in this game, it has been designed to only be done by multiple players so trying to do it alone is extremely tedious.
My main two ideas for how to solo the event were to put the enemies to sleep with a panflute then hit them to draw aggravation and just do that to try to keep them all distracted or asleep as long as possible. Or just surround the moon stone in walls so the enemies can't actually reach it. But I looked on the wiki and it was like blah blah walls don't work the enemies just blah blah or something and it really doesn't make sense why walls wouldn't work.
Like, if you surround the moon stone in two layers of fully upgraded stone walls, I can't imagine them being able to break through before the event ends unless they all focus one part of the wall down. Or there is some kind of mechanic in place which melts the walls so the enemies have a fair chance of getting to the moon stone but I doubt Klei put that failsafe in. Has anybody actually tried using walls to solo the event?