I had a great time playing against Alyan, theTomasPat, nobi and others today and this is how it started:
I went to Strasbourg Custom 2 and started racing just by myself, so that people would see that somebody is on that server. It took like 3 races for others to start joining in and then we had a total blast, at least I did.
When you let people race on your server by themselves, they have something to do while waiting others to join. I think that's the way to help people meet to play STK online.