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.
If you fall for someone's trick the first time then they are at fault.
Are you going to mess with me again? Fool me once, shame on you; fool me twice, shame on me.