While some Sectionals are yet to be played so the specific teams aren't known, as of today, which sections go in which flights and the match schedules have been published for the following divisions/levels:
I'll try to post updates as more of the schedules are published. And I'll update my Nationals Schedule with these links as I have them.
So if your team won Sectionals and is headed to Nationals, you can now go see what sections you'll be playing and what your match schedule is. If you are willing to do a little leg work though, you can go lookup who won each section and determine the teams you'll be playing too.