Step 2: Sewing the top with the drawstring
Lay the drawstring along what will be the open end as shown and fold the fabric over. If you have pins to hold it in place, that would be useful. I didn't have any so just gripped it as I sewed it.
This can be done easily with a sewing machine, too, but I don't have one of those. I like to get down to the basics as I'm a bit of a rugged sort of chap. :D
This line of thread you'll want to do the most carefully as it is the only one you'll see when it's finished. I found this out after I'd done it but hey ho, we learn from our mistakes. ;)
After you've gone across to the end, go back again to fill the gaps, as seen in the third piccy.