this is a basic requirement. Create an item on a list (for example, the list is for events that are coming up) and Flow should automatically create a SharePoint site to coordinate that event
This can be done with using the standard REST APIs within SharePoint 2013 Workflows in SharePoint Designer, which works every time.
I then applied the same JSON logic within a HTTP Call in MS Flow & get an error (open thread here) so at the very least would expect this to work.
However, the very simple ability to have an MS Flow extension that could do this with ease, along with additional new site setups such as: - Setting unique permissions & creating bespoke Visitor, Member, Owner groups - Populating those groups with users (ie if triggered from a list, uses a People Picker field in Flow to then update the newly created groups) - Allow switching on/off of Access Request settings - Ability to set bespoke permission levels for to newly created groups