Is it possible to invite a friend to team up with in a team/doubles game and leave the rest of the spaces public so anyone can join? I want to team up with someone in a doubles/team game but leave the other team open for anyone to join. Is this possible and if so how do you do it?

No, it is not possible.  Such things have been suggested in the past, but have not been implemented.

The best you can do is be on at the same time and have one person create it and the other person join. 

Cheers for the reply. Oh well, i'll have to do what you suggest and hope for the best.

It helps to post a message in the open game requesting a spot for the teamate you'd like too.