me after i got mecha 7:
"yay, i got the min!"
"...wait"
"oh dear god no"

and so i made this solution. every input goes through a bonder/debonder that breaks off a single salt atom and adds the other two atoms to a waste stick. this lets it slowly construct the large output one or two atoms at a time, duping air from the waste stick and occasionally moving it to avoid collisions. thanks to the waste, this has a comically large actual area score of over 10000 and takes irritatingly long to run, but i'm not going to work out how to do it better.