For general discussion between ESL teachers.
A forum is an online place where persons can start a discussion on any topic. It will depend on you to choose a category for discussion. You can simply type online "how to make a forum" and find forum creation steps.
To create your own forum is very easy. There are some built in websites which can help you to create forum within seconds. fro example create forum sites. This can be applicable If you are not very technical. Choose the version and the theme that fits more about your forum. PhpBB3 forums are perfect for beginners.