Weave the four bars and bring the needle up in a corner fabric hole. Insert needle from back to front in the center of the left woven bar (A). Form the twist as needle passes under first stitch on the way to the adjacent woven bar. Insert needle from front to back in the center of that bar (B).
Pull needle through and pass it above extended thread as it returns to same corner hole (C). Repeat on all sides to form the center circle (D).