Creating sites - SharePoint online using https://contoso.sharepoint.com/_layouts/15/CreateGroup.aspx

[spowaffle]

SharePoint Community, 

I am looking for an answer to manage how and who has the ability to create sites in SharePoint Online. I have some users using the URL - https://contoso.sharepoint.com/_layouts/15/CreateGroup.aspx to create communication sites.

While I would like to let a specific set of users to be able to create sites, I can't let everyone in the organisation create sites at will. How do I go about achieving this? Also, to make matters more confusing, some users can access the URL alright, the others can't. 

I understand this could be related to the Office 365 groups creations and administration around it as well but I am specifically looking for an answer to my question above. 

Thanks

[#2]

@spowaffle - I cannot believe no one answered this question for you.

The quick answer is - Create a SharePoint Security group at the top level of the site collection. Add the people to it. Give that group Full Control permissions. The people in the group can then create sub-sites under that top-level site. But no one else can.

Alan