Hem the 2 short edges of the long rectangle. Do this by sewing ¼ inch all the way along the short edge. Fold the fabric towards the wrong side along the sewn line, press. Fold the fabric again towards the wrong side, and press. Sew along the folded edge with a straight stitch in a matching colour to the linen.
STEP 2 Fold the linen in half right sides facing together, and pull one edge of the fabric up so it is over-hanging by 31cm (diagram 1). Fold over the extra fabric down (diagrams 2 & 3). Pin the sides in place and sew a seam along both sides (diagram 4). Sew each side again with a zigzag stitch; this will give strength and stop further fraying of the seams.
STEP 3 Pull the pillowcase the right way around and insert pillow form.