The league coordinator should have a list of folks that are not yet affiliated with a team - but want to be. If the local organization has a captain's meeting prior to the new season - you should go to that and ask around.
There is no substitute for getting involved in any organized events to get your name out there. Try any tournament or ladder type league you can find. If you are good enough for your rating - somebody will pick you up. Joining a team would likely lead to quicker success than forming a team. A totally new team should be prepared to take some serious lumps.
I got lucky and was asked to join an established 3.5 team (while I was still rated 3.0) that I stumbled across at a local park. They practice every wed and sun - as long as the temp is above 40F. I showed up each possible date for about 1.5 years and filled in where ever the captain of the team needed me. Eventually he asked me to be on his team (even though he had 14 players) just to keep me from joining another team. We have won the local USTA competition now 7 years running (two for me) - and 9 out of the last 12. Unfortunately - we get creamed at the State Tourney each year.
This year I played on that 3.5 team and a 4.0 team - that was formed by one of our 3.5 teammates that was bumped up. It had essentially the best players from the lower level and a couple of higher level folks we found at the captain's meeting.
Keep going out and looking for folks to play with - when you find anyone with a team affiliation - do not keep it a secret that you desire to play team tennis.
I personally have a blast - and look forward to each practice and each match. The road trips are the best.