In no time flat phrase
Very quickly; in a short period of time
The incident happened in no time flat.
He is such a genius. He can solve this complicated equation in no time flat.
Very quickly
Very fast.
Quickly and effortlessly
The origin of this phrase is not clear.
A humorous way of saying that what one has said is just what they acknowledge and may not be entirely accurate
Mike: Have you returned from your vacation on the beach? Your skin seems to get tanned.
Jenny: My skin is always dark. That's my story and I'm sticking to it!