Hi Mr.Z'
The sticking point here is a process called imposition—placing the pages in the right order and correct orientation to be arranged logically in the final product.
Your description implies that the booklet will use A6 paper, and will be folded to produce a booklet with A7 size pages, 4 on each sheet.
Three sheets will then provide space for 12 pages of content—a cover page, 10 pages of content, and a back cover, laid out four pages to a two-sided sheet in this order:

While there is no imposition software, to my knowlege, written for direct use with Pages, there are several applications that work with a pdf file to reorder the pages of that file to correctly appear on a multi page booklet. You'll find them at the App store.
Regards,
Barry