Hi, can anyone tell me how to build a floating pond island (as seen in the Gardener's World Berryfields wildlife pond). I tried the BBC gardening website and it had no instructions!!!

Google and Ask brings up a lot of info on wildlife ponds and islands, but not the floating kind.
My village is thinking about having one in our community pond to give the birds/ducks a haven from the local fox population and I remember seeing them make one on Gardeners World... but can't remeber the how!

It seemed to be a raft made of natural materials... but what ones? Are there instructions somewhere on how to make one? (or is there somewhere we can buy one? Although making would probably be more fun). I do remember they attached ropes to the sides to keep it in place, but that's about it.
Thank you!