I used cardboard that came with album refills and altered it with paper, ink and stickers. For the inside of the smash book, I cut paper to size and hole punched it. I didn't want to order a premade smash book, because I saw it as an opportunity to clear out my paper stash and use the stuff that was sitting for years and years.
My pages are sturdy because I am using cardstock and adding paper to it. It is a work in progress that will evolve as I add to it.
No rules! Make it yours!