Here we go...
The little composition notebooks are 2/$1.00 and are about 4-1/2" x 3-1/4".
Measure the top and sides at 1" from the corner and draw a diagonal line on the cover only. The corners are rounded so just get a close measurement, it won't be exactly perfect. With a pair of scissors, start cutting pages, 5-6 at a time using your cover as a pattern.
This goes very quickly, you literally have this part done in under a minute! It takes longer to clean up the clippings!