I have a Slack workspace for my office, and want to create a channel for a particular project, and add the client to that channel. But I don't want to client to see our 'General' channel etc. Is there a standard way to approach this?
There are two features that do this, that work in slightly different ways:
Slack Connect: You can add someone from outside your workspace, even if that person isn't already signed up to Slack. On the free plan, you can message them one on one. In the paid plans, you can also these users to channels.
Adding "guests" in Slack: This feature is only available for paid plans. You can invite guests, and they will not be considered full members of your organisation. If a guest is granted access to only one channel, they are called a one-channel guest, and there is no additional charge. If the guest is granted access to multiple channels, they are called a multi-channel guest, and the workspace manager pays for them as if they were a regular member.
I think that the feature you're looking for is maybe "slack connect"
you could create a special channel that allow you to send external invite. (this require admin moderation)