I've attempted to use the sandbox-exec utility, but didn't have the stamina to get a working sandbox file written.
In general, I'd like to be able to sandbox more things. I'm using the app store version of slack because slack doesn't really need access to all of my files.
I haven't tried to use it in anger, but I believe this is the likely starting point https://developer.apple.com/documentation/xcode/configuring-...