If you are an introvert, how have you made friends?

My son went to a small and intimate preschool with mandatory community service and frequent gatherings. As a result, I got to know a lot of parents and made one close friend and several casual acquaintances.

He switched to a larger public school last Fall and he has done well but I am adrift It is like most public schools - it draws from the neighborhood but parents don’t spend much time at the school. I have talked to a few people but haven’t made any casual connections.

People seem to interact a lot via Facebook but I am not particularly good at engaging with people online. I did join a local moms group but it is aimed mostly at moms with younger kids. As I get older, I feel I am getting more introverted which is not helping. I am happiest pottering around my garden but do occasionally crave company! (I am a INTJ Libra if that matters.)