1 Cut the waistband from the jeans as neatly as possible. Lay the jeans flat and trim a rectangle, 29cm x 33cm, around one back pocket, avoiding any thick seams. Remove the reinforced inner leg seams, leaving a 1.5cm excess on either side and save them to use as binding. From the remaining leg, cut another rectangle, 29cm x 33cm, and two pieces, 11cm x 29cm.

2 Sew the two larger rectangles, right sides together, along the bottom edge, leaving a 1cm seam allowance. Open out and reinforce with topstitching, 5mm from the seam. Lay the joined fabric flat, face up. Take one smaller piece of denim and pin the centre of one short edge at a right angle to the seam, right sides together and matching up the raw edges. Stitch and fold to make a ‘T’ shape. Repeat for the other end of the seam to create a cross.

3 Pin the arms of the cross, right sides together, to make a flat bottom bag, then stitch and turn right sides out. Cut stiff card, 10cm x 26cm, and wrap it in duct tape for support. Slip this base into the bottom of the bag.

4 To make the lining, create a second bag from cotton and leave it inside out. Slip the lining into the bag, making sure the corners are level. Pin and tack the top with the raw edges together. Join the saved inner leg seams end to end and, if necessary, make a fabric loop the same size as the top of the bag. Trim the excess thickness away from the joins to avoid a lumpy finish.

5 Pin the loop to the outside edge of the bag, matching the raw edges, then stitch with a 1cm seam allowance to bind. Fold the binding loop up and over the top edge of the bag, tuck under 5mm and slip-stitch the edge of the binding to the inside of the bag.