Okay, you should cut out 2 squares, 9 by 6 and your zipper.
Fold a hem to prepare for sewing on your zipper. Fold on the 9 inch long side.
Pin them to your zipper.
get your zipper foot out and start sewing along your hem.
so now you should fold the sides together so that the zipper is inside out. And on the opposite side of the zipper, sew the bottom shut.
And you should have a tube, something like this.
Now most important before you start the next step: Open up the zipper about halfway. Trust me on this...there'll be less swearing if you do! So do it now.
Now you're going to flatten it out like this. Cause this is where you sew the ends together.
Just straight down along the 6 inch side.
something like this,
Now puff it open, (still inside out) and pull out the corners so that you can draw out the triangles or corners. I used about an inch from the tip of the corner, marked it, and pinned it. Do this for all 4 corners.
something like this.
I set my machine to the shortest straight stitch and now sew along your mark. Closing off that corner.
Afterwards it should look something like this.
cut off your ends, but don't cut where you've just sewn. Or you got nothing.
Now this is where the open zipper helps: Turn your bag inside out and you should have a fabric box bag!
Fabulous, now go make a ton!