In the same way that you join into a picot, work joining picots into the holes of a hem-stitched hanky. For the corners work a join nearer the corner and work a longer chain of 5 - 5 - 5 to go round it.
You could also make a small fabric bag for your tatting and decorate it with this chain edging. Make holes at half-inch intervals by using a stiletto like a Victorian lady, or a darning needle. The chain can then be joined into these holes. See picture with Beginner Butterfly Pattern.
Ring: 3 - 3 - 3 - 3 RW leave ¼″
Ring 1: 3 - 3 - 3 - 3 RW (Reverse Work,
i.e. turn work upside down)
Repeat from * and continue to work in zigzag fashion, leaving about 1/8" of thread between each ring.
Big and Little Rings
Small ring: 3 - 6 - 3, leave ¼″ thread
To fit round a corner, say on a hanky, do small ring, big ring,
Ring and Chain
Ring 1: 3 - 3 - 3 - 3 RW (Reverse Work, i.e.
turn work upside down)
Starting Ring: 4 - 2 - 2 - 2 - 4 RW