这是个省略句,译文：他们站在一起聊天,怎么样最放松最自然就怎么站.
they stood chatting together as easily and naturally as easily and naturally could be.
再如；
He ran away as fast as his legs could carry him.
He ran away as fast as (fast)could be.
He ran away as fast as he could (run).
他尽可能快的跑走了.