You will need the seam allowance all the way around your pillow, so if you make a square that is exactly 14"x14" your pillow form will be too big. I prefer to have more than a 1/4" seam allowance on a pillow, as they have a tendancy to get tossed around and not handled gently, especially if there are any children around. You can also make a 12" finished square and add a 1-1/2" sashing/border strip all the way around that will be what is actually going to be what is stitched in the seam at the edge of the pillow using a 1/2" seam. Hope this makes sense!