How do I format a link to a remote lemmy community that allows someone to subscribe to it directly from their own instance?

An example of such a post is here This is a post made for a community on, posted to and viewed through my instance

Whichever instance you view it on, the link formats so that you can subscribe to it directly from the instance you are viewing it on.

I’ve tried using /c/communityname formatting, but that doesn’t seem to work.