One of our graduates, Robyn Crosland, of the Central Coast Permaculture group in NSW developed a “Tin tower worm system” which incorporates a raised worm farm, a liquid manure bay and a herb garden on top. The system works beautifully. You can make it out of old oil tins, insert a tap in the lower tin, put weeds in the middle tin, a worm farm in the top tin and then site a pot of herbs on top. We use the top pot as our intensive care bed for rare or special plants.
Sometimes, we put a tube in the top tin for easy feeding of the plants and then plant out the top tin.
We don’t bother to put feet on the tins anymore, we simply use another tin at the bottom for support and insert weight eg. water filled reused containers or bricks. See here a recent discovery on how worms digest matter.