I've also made a few of these from onion bags. I don't know if places other than New Zealand get their onions in these bags, they are mesh sort of bags.
Instructions for these here.
Ok, this is what I did. I sewed up the sides of the bag and turned it right side out. Then I folded a piece of cotton fabric across the top of the bag and sewed it all around. I think this will give it stability. Then I made handles in the usual way (fold fabric in half, press, open; press each raw edge to centre line, fold in half, sew down) and sewed them on. Easy!
I also use on on the back of the bathroom door for the bath toys.