First, cut your paper 8" wide and 7" tall. Go in 2 1/4" on each side of the 8" wide piece and score all the way down. (I use my paper trimmer and a bone folder to do this...great if you don't have a board just for scoring.) Then, score 1" in on one un-scored side and 1 1/2" in on the other un-scored side (all the way across your paper).
Next, you'll want to cut out the scored corners (see photos).
Using a corner rounder, round the four corners as shown.
Fold in one side and adhere the other side to the top.
Fold the bottom flap up and adhere.
Now you have your finished product! Another fun thing to do would be to use a border punch on the top flap so that you have a decorative touch.