How are NFL schedules determined with so many teams vs. games played?

each team plays teams in their division twice, plus each team from another division in an opposite conference once (this is on a rotating basis). They also play each team from a division within their conference once (also on a rotating basis). They then play the teams in the other two divisions within their conference that finished in the same place in their division (for instance, 1st vs. 1st, 2nd vs. 2nd, etc.)