With RS facing, using smaller straight needles and 2 strands of yarn held tog, pick up and k6 sts along side of Bottom of Bag (Garter St ridges). Work even in Garter St until gusset, when slightly stretched, reaches to cast-on and bound-off edges of bag, end on WS. Bind off. Sew sides of Gusset to edges of body of bag. Repeat on the other side of body of bag.