Doesn't really matter. Divide them into however many you want. You could plant them all singly if you have the time to waste. :) They'll eventually grow into large clumps anyway. And if you let them go to seed they'll be all over the place.

Rodney

I use a serrated knife to divide my chives. I know it probably sounds terrible to you, but they don't mind.

I've used a garden spade in the garden many times to rather indelicately divide clumps. Robust growers never care much how you give them space. ;)

FataMorgana