I made this little notebook (mine is 2" x 4") from a used manila envelope. It utilized only things I normally throw away and I think the postage makes an interesting cover.
Choose which page to use for the cover. Reinforce the inside by gluing card inside cover with stick glue.
This is what your cover should look like at this point.
Stack your pages. Punch two holes through the fold of each page.
Sew the pages together.
Using stick glue, attach the back page to the inside cover. You could do the same with the front, but I choose to attach only the back.
Using stick glue, attach a small scrap of paper to reinforce the "spine" area.