Seams
Pin piece A over piece B and the border of the window over the stitched fabric to frame the motif. Machine stitch with blue thread, making a straight seam 4 mm from the edge of the window (see diagram).
Using a pair of pinking shears, cut out of the oilcloth four squares measuring 13 cm each side.
Pin these squares on to each corner, after having placed a seashell between the blue fabric and the oilcloth.
Machine each square with blue thread, making either a straight seam or, if you wish, a fancy seam, if this is possible with your sewing machine.
Sew the oilcloth all round the square 1.5 cm from the pinked edge, ensuring that the blue fabric and the stitched fabric are also caught in the seam.
If necessary, reposition the seashell if it slips.
Before lifting the presser foot, insert the needle in the fabric at each corner of the seam before turning so that you obtain a right-angled seam.
Stop the threads at the back and secure them firmly