Hi @Chris1969 ,
Could you please share more details about your scenario? What do you mean by "new books are received"? Do you have a data table to store the books inventory?
Assuming that you have a SP list to store the books inventory, when new books are received, book inventory manager would add each book into the list. If so, you could create Flows applied on that list to create Teams channel automatically. But speaking of SP site, is it necessary? Why not create Libraries or even folders in a specific library? Creating sites is not so easy using Flow, you will need to leverage SharePoint REST API to achieve that need.
To be clear, below is a Flow I created for demonstration:



With this flow, when add a new row in the "list1", a new Teams channel and a folder would automatically be created. Channel name and folder name are both basing on the Name column value in the list1.
But if subsites are necessary in your scenario, please refer to below blog which contains detailed process of creating a Flow to create subsites:
https://www.annajhaveri.com/sharepoint/create-a-sharepoint-online-subsite-from-power-automate-flow/
Or if you need to create a library, you will need a "send an Http request to Sharepoint" action, below is a blog for your reference:
https://www.kkit.com.au/post/create-a-sharepoint-library-with-flow

Hope this helps.
Best regards,
Community Support Team _ Jeffer Ni
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