You can invite more than one participant to a single time by opening an Open Interview Spot and clicking the toggle to Group Session, then specifying the number of participants that can confirm for that single time. When your total participants have confirmed, the time will no longer appear in your screener as an option.
Then you simply invite and confirm participants as you normally would. You can also create backup spots as you normally would. Make sure to edit the new group session invite and detail emails as well: