Dynamic item pages url

I’m migrating a site from squarespace and this has a flat url structure ie domain.com/page1 etc

There are a lot of pages and I was hoping to use the cms to create dynamic item pages quickly. However, the cms demands that item page urls include the collection name as the root ie domain.com/collectioname/page1

It does not appear to allow variables immediately after the domain unless I’m missing something? Some of these pages have very good authority and I don’t want traffic to tank as a result of the migration which did happen on another site even though I did all the redirects properly including in search console.

It will be so much extra work to do this as flat pages so can anyone offer me any solutions?

thanks in advance