掌を返す

phrase

to do something easy as turning one's hand over / to flip-flop; to do an about-face; to flip over one's hand

彼は掌を返すように問題を解決した。

He solved the problem as easily as turning his hand over.

意味（1）

to do something easy as turning one's hand over

Kono mondai wa kimi ni totte tanagokoro o kaesu yō da.This problems seems as easy as turning one’s hand over for you.

意味（2）

to flip-flop; to do an about-face; to flip over one's hand