Step 2Measure and cut "apron" to fit
iImage Information

The "apron" (cut folder) should, when closed, measure approximately 1/2" more than the width and 1/2" more than the height of the book. This catches more spills and allows room for the rickrack so it doesn't obscure the text. This margin isn't so large, on the other hand, that the apron will be shredded by sticking out when the book is closed.
A paper cutter is ideal for cutting the folder super-square, if you have access--if not, a ruler and Olfa knife will do the trick.