Once you've set up the Teams app in Slack, you'll be able to start a call by simply using the command /teams-call. You'll also be able to see who's already in a meeting before you hop in and also join calls from Outlook or Google Calendar reminders in Slack.

However, you can't take part in Teams calls entirely within Slack, at least for the time being. If you join one from a Slack channel, the call will open up in Teams instead. In addition, you'll be able to dial phone numbers via Zoom, Jabber, WebEx, RingCentral and Dialpad directly within Slack. At least this might make getting things done while you're stuck at home a little easier.