Rotate the Cardstock back to the original position (which is shown in the picture); you are going to use a good paper scissors and snip the scored lines at the bottom along the 1", 5", 6" & 10" score lines up to the bottom of the horizontal score lines.
Next you are going to trim the top of the Cardstock along the top horizontal line. Then go down two more horizontal lines (2 inches), trim up to the 6" score line. (You are making the flap that will close the box) Then starting from the right, trim the two 1" squares. (You should have two 1" score lines, that are your flap.)
Finished 4x4 Box