Cut yarn, leaving a tail of approximately 18 inches. Thread it into the large-eyed, blunt needle.
Place the pieces right side facing up (that's the side you want to show), and fold it over. Insert needle through the corner of the folded sock and draw yarn through, pulling needle out at the corner to begin sewing.
Sew one edge to the other, matching stitches across the side edges, and weaving the yarn though the stitches on one piece.
At the end, work a few inches of yarn woven through fabric to secure (you won't need to make a knot.)