For each napkin cut the following:
(1) 18" square of linen
(2) 4" x WOF strips of printed fabric
Cut the ends of your 4" strips at a 45° angle. Using a 1/4" seam allowance, sew strips together end to end. You will need to offset the edges by 1/4" inch.
Press open your seam allowance. Press your strip in half lengthwise, wrong sides together. Press one side in half again bringing the raw edge up to the first fold line.
Place the end of your 4" strip at about the midpoint of your square with the folded edge away from your sewing edge. Start sewing about 3" above the bottom of the square with a 1" seam allowance.
Sew until you are 1" from the edge of the napkin. Turn your napkin 90° and sew in reverse off the edge of the napkin.
Check that you now have a perfectly fitting continuous strip of binding to stitch down on the final side. If so, trim 1/4" from the sewn line and press your seam open. Sew the remaining binding down with a 1" seam allowance slightly overlapping the end points of your previous seams.
Fold your binding over the edge of the square to the back of your napkin. Your square should tuck right into your folds. Miter your corners and pin in place.