How to add a non-Pomona user to your Slack channel
Click your workspace name in the top left, then select Invite people to [workspace name] and choose Multi-Channel Guests (for 7C guests) or Single-Channel Guests (non-7C guests).
Provide the necessary information, and under the Invite to channel box, choose your channel(s) they’ll have access to, and set your desired time limit for the guest access, and click Send Request.
3. The guest will receive an email with an invitation link to join your channel(s).