http://vrici.lojban.org:3001/
Just enter your email and you will get an invitation.
The Slack chat is fully synchronized with Lojban IRC chat but additionally has history kept for a few last days.
Which is beneficial if you can't be connected 24 hours a day.
You can ask a question, go offline, return in a day and continue reading the chat from the point you left. Answers to your questions will for sure be available by that time.