I wanted to show how I make button closures with a hair elastic on my junk journals. There are many variations on this one and you can alter it to suit your preferences.
1) Using the 3/16" punch on my Crop-A-Dile (any hole punch this size or larger will do), I make a hole in my back cover, centered from the top and bottom, and about 1/2" from the edge of the book. I put my hair elastic through the hole, from the inside (see pic 1).
2) I then take the elastic end that's on the inside of the book and 'thread' it through the loop that's on the outside (see pic 2)and pull it tight.
3) To tie my button on the front cover, I punch two small holes about 1/4" from each other, at the center of the cover from the top and bottom and about 1 1/4" away from the edge (this distance varies based on the size of button you use, just determine that distance by what looks good). I use light gauge wire or twine and either tie it off on the button or inside of the book - see pic 4 (this too depends on whether or not I want to add a brad or gem on the button to hide the tie off). If I tie it on the inside of the book cover, I glue a fabric flower or round piece of punched paper, or brad, etc to cover the tie off, especially if it's wire. If it's string it can look decorative if tied in a bow. But make sure you knot it securely first.
4) I don't tie the button snug to the cover, but leave some 'give' so that the elastic will fit under the button once closed.