A space for guest users?

I just set up a server for mattermost with the intention of testing it out before rolling it out to my users.

I need to have a space where I can interact with a few freelancers, such that they cannot interact with each other. Is there a way to set up something like this?

Currently in Slack I use external connections and 1:1 messages with them.

Assuming pro/enterprise, you can create a channel for your communication that only you and them are a part of. Then add them as a guest user with just access to that channel.
The guest will be able to communicate in that channel, and would only be able to DM members of channels they are a part of.