The template takes advantage of the little bit of extra fabric you get around your designs when printed. I highly recommend you place a light colored, thin (3 pixels will work), line around the outside edge of the pillowcase to use as a sewing guide.
If you are doing an over-all design you will only need the construction part of the instructions.
I will be posting all designing, and construction, instructions on Flickr shortly; and linking them here.
Feel free to "zoom" and grab a screen shot for reference.