At the What's Next at SURFconext event of March 2018 we created a demo-flow.
COmanage, part of the current SCZ-setup, lets administrators define several types of invitation flows. You can find more about that in the documentation.
When a research collaboration is o.k. with people signing up by themselves, they can publish a link, for instance attached to a "Sign Up" button on a website.
For the demo we used this self signup invitation URL: https://comanage.pilot.scz.lab.surf.nl/registry/co_petitions/start/coef:309 .