"The lizards suddenly eat the ants."
Translation:도마뱀들이 갑자기 개미를 먹어요.
I think technically they can be placed anywhere (except at the ending where the verb comes), similar to object, subject, etc.
From the howtostudykorean.com website:
"The best part about Korean adverbs is that they can essentially be placed at any place in the sentence."
However, I think some word orders sound more natural than others, but I'd be happy too to know if there is a rule for that.
Personally, I started to feel over the course of my study which order is more natural than the other.