Knit folded bag

I knit a giant rectangle with the length three times the width.  Then folded in ends and sewed two seems up sides with mattress stitch. I cast on 38 stitches for width. Measured 12″ and then knit for 36″ length. 

Garter stitch (knit both sides) for entire thing. Then made handles with casting 9 stitches and knit stockinette stitch (knit 1, purl 1). For 7″ length. 

I sewed the handles to the tips of the bag. 

From the pattern;