Laughably [Something]

へそで茶を沸かすくらい____。

So ______ that I could boil tea with my belly button.

Of course, this is a saying, because why else would you say something like this?

Apparently the idea came from how when you laugh crazy hard, your belly button looks like boiling water. Another possibility is that it creates so much friction you could boil water. Where the tea comes from, I'm not sure.

Put your favorite adjective in there.

へそでちゃをへそで茶を沸かすくらい簡単だ。
Laughably easy / Stupidly easy.