Cut the leg off below the crotch of the jeans.

Open the front seam, and pin it flat.

Sew along the pin lines.

After you've sewn the center, cut off the excess fabric.

Repeat on the center of the backside of the jeans.

Pin and sew a 1/2 inch seam on the bottom.

Once the bottom seam is sewn, match the side seam with the bottom making a point.

Measure 3.5 inches across and mark a line.

Pin and sew along the line. 

Cut off the point or leave it for extra support.

Repeat on the other side.

Turn the back right side out and you have a boxed bottom for your bag.

Pin one side of the zipper just inside the waistband.

Sew that side using a navy or blue thread.

Open the zipper and pin the other side. Sew in place.

Cut a small piece of twill tape and slide it through the D-ring. 

Pin it to the top of the side of the bag and sew into place.

Trim off any extra twill tape.

Clip a decorative strap to use as your handle. 

Decide on the finished length and width.

Split it in half and add extra for seams and attaching to the bag. 

Sew the two strips together on the short ends using 1/2 inch seam allowance.

Press open the seam open. 

Fold the fabric in half lengthwise with right sides together.

Stitch with a 1/2 inch seam allowance.

Turn the fabric right side out and stitch it to the bag.

Fold under the raw edge and loop it through the D-ring and sew it back onto itself .