OSDev.org

That's exactly what it covers - how to manipulate page tables, either the current one or another one. You should read the articles I linked to there.

You can keep an array of CR3 page directory values. If an element contains 0, you can add a page address to create a new directory.

You just need to keep track of free physical pages with a bitmap at least.

Then with your visor page table you can map around unmapped pages to initialize a completely new page directory.