Find a side plate that measures about 1/2 inch larger in diameter than your lunch box (or, if your lunch box is square or rectangle cut a shape 1/2 inch larger) from each of the patterned cotton fabric, the thermal layer and the lining. I used a 7 inch circle side plate.
Cut a rectangle 8 inches deep by 23 inches long from each of the three fabrics.
Pin, right sides together, the long edge of the rectangle to the outside edge of each of the circles and sew a 1/4 inch seam with a sewing machine using a strong, good quality, cotton thread. Zig zag around the outside edge of the seams to provide extra reinforcement.
Pin the right sides of the short rectangle edges together. Sew with a 1/4 inch seam and again, zig zag the outside edges for reinforcement.
Keeping the lining bag with the right side on the inside, pin to the thermal layer around the top edges. Sew and zig zag.
Pin the velcro along the inside edge of the top, about 1/2 inch from the top edge, and sew with a strong thread.
Turn the patterned cotton fabric layer so that the pattern faces outward, and place the lining layers on the inside, pinning along the top edge. Sew along the edge with a 1/4 inch seam.
Carefully place your length of ribbon along the outside edge of the bag so that 1/2 inch of it shows. Pin the other edge of the ribbon on the inside, taking care that it doesn't cover the velcro layer. Sew with a matching thread just on the inner edge of the ribbon on the outside of the bag, through all the layers.
Sew your brass chain handle on, or alternatively, sew on some matching ribbon and tie the handle on with that.
Embellish as desired with steampunk cogs and gears and a few old keys, if you have them. Super glue makes a short job of this.
Mum of three, daydream adventurer, OU Life Sciences graduate, occasional crafter, ex-pat Canadian & quite possibly Britain's most northerly food blogger.