I started with using photos that were all the same size.For this mini, I used 3x3 square photos that I'm sure I stole from Instagram.
Then I took two pieces of cardstock that were 3x6 and glued them together to make the "cover." I cut small holes where the bend would be and at the ends of one piece of cardstock so that I could thread ribbon through the top, string through the back, and a brad in the front. I added those elements before gluing the two pieces together so they would be secure but also sort of hidden on the inside. The book is a little "poofy" so the string helps to keep the book closed.