Summary:  Eight seed stitch rectangles sewn together and felted produce a sturdy diaper bag.

Materials:

• 635 yds. yarn in Color A; 381 yds. yard in color B
• Yarn needle
• T-pins
• 15" x 5 1/2" piece of heavy plastic, needlepoint canvas or cardboard, to keep the base of the bag rigid and flat (optional)
• 6 1/2" x 16" piece of fabric, sewing needle, and matching thread, for lining bottom of bag (optional)

From Knitting for Baby:  Making this bag is a simple matter of knitting eight seed-stitch rectangles ..., plus two straps, sewing them altogether (sic) into a bag shape, then felting in the washing machine. ... The pieces of the bag are knitted in seed stitch for thickness and durability and sewn together before felting so that they will all shrink and felt at the same rate.