Remove the original door net pockets from the car using the correct Torx 20 bit.
Place the pocket on the piece of leather and draw around it with the chalk.
On the opening side of the pocket extend the line by 10mm so you have more material than required and cut the leather out with some decent scissors.
Fold the extra 10mm of the leather over a length of eleastic ribbon and sew a straight line from one side to the other either by hand or with your mum's sewing machine.
Remove the old netting from the frames by un-clipping the inner bracket and pulling
the old net off. Place elastic up between the top of the 'V', measure how much
gathering you would like and adjust to the elastic to suit.
Sew the elastic to the leather to secure the adjusted length and cut holes with a
punch or a blade to fix the leather onto the frame.
When you are happy with how it looks trim the leather for a good fit and Reattach the inner to the outer bracket clamping the leather in between.
Refit the pockets back onto your Smart and admire your work.