Pages -Inserting additional pages

I have created a book but want add a couple of additional pages within the current text. The document contains numerous photographs and text boxes so is not a text-only document. Most of the insertions are "around" or "none" in Document Layout and some are "Stay on page" with others being "move with text".

The layout so far is exactly what I want to retain but I need to insert a couple of additional pages about ⅓ of the way through the book!!

I have looked up "add a page" and tried it on a trial Pages document with some photo images and draft text and using

it worked with the layout remaining the same on subsequent pages.

However, when I try the same on my main document everything shifts on subsequent pages but not in the same layout.

Anybody tell me what I might be doing incorrectly please.