First, you will need to use your scissors to cut along one of the skinny sides of the box to open it up. The best boxes are the extra large ones from Costco or Sam's Club, but any kind will do.
Next, you will measure a rectangle that is 10 inches x 13.5 inches. Try to position the rectangle to avoid any fold lines going right down the middle, since you will be adding your own there.
Cut out your 10" x 13.5" rectangle
Line your ruler up at the bottom and put a small line at 6.5" and 7". Repeat the same measurements at the top. This marks where the spine of the book will be.
Connect your 6.5" and 7" marks at the top and bottom with two vertical lines using your Sharpie.
Line up your ruler with the Sharpie line on the right. Holding the ruler down tight, lift up the cardboard to make a crease at the ruler. Rotate the box and repeat on the other Sharpie line.
Reinforce your creases by folding it closed like a book.
Choose any colored or patterned duct tape and wrap it around the spine (front and back) to reinforce. Make sure the spine is centered in the middle of the duct tape.
Re-crease the folds you measured.
Open your book and turn it vertically. Line your ruler up with the left edge and mark at the following spots across the inside of the spine: 2", 3.5", 5", 6.5", 8"
Using your Xacto knife, cut rectangle-shaped holes on the lines you just marked. You must cut a hole, not just a line, or else the yarn won't be able to go through.
Next, make a stack of your 9x12 white papers and fold them in half together like a book, so they are now 6x9 in size. Repeat with the manila papers.
Line your ruler up along the fold of your white folio (folded stack of all white papers together) and mark at the following measurements: 1.5", 3", 4.5", 6", 7.5". Repeat with the manila folio.
Using your scissors, cut triangle-shaped holes at each mark on the folios. When you open the folio up, the holes should be shaped like diamonds. Repeat on the manila folio.
Set the white folio aside. Open the manila folio and line the diamond holes up with the holes in the cereal box. Imagine the top hole is #1 and the bottom hole is #5. Use a piece of yarn to sew.
The inside should look like this. Secure with a double knot and cut off extra yarn, leaving 1 inch tails on each end.
Close the manila folio. Open the white folio, place on top as shown, and line up the diamond holes with the holes in the cereal box. Repeat the same sewing steps with your other piece of yarn.
The finished product should look like this on the spine. Well done!