2nd Season 12 team League Setup

Hello

I’m the commissioner of a 12 team league which has two 6 team divisions.

13 week season followed by 3 week playoff

How do we decide which the divisions for our 2nd season?

My suggestion is the 6 teams which made the playoff go in 1 division and the 6 teams which missed out go in the other division. Is that right?

What do other 12 team leagues with two 6 team divisions do?

Any help will be greatly appreciated

Regards
Chris