This instructable shows how I got round to making it. This mainly consists of a series of diagrams combined with a few actual photos.
I hope you may find this useful.
Share & Enjoy.
Step 2: Flatten required area
Step 3: Create shuttering for concrete base
To make the ring I simply dug out a small channel in the ground, for the required shape, and placed small pieces of 4mm plywood (I had some scrap from a previous project) to create some shuttering. To get the sides of the pond level I used a long builders level. If a piece of plywood was too high I hit it with a large hammer/mallet until it was in the right place.
Step 4: Remove concrete shuttering
It's not a good idea to leave it in as the wood could splinter and then puncture the pond liner.
Let the concrete go off for a few more days. Take a day off, go kayaking, partying etc.