The hole is now finished. But, I am worried that the steep banks will crumble if people step too close to the edge. Here, I have started placing wooden boards around the edge and use these to obtain a level. Having ascertained that the boards are level I placed soil each side of the boards making a gradual slope into the pond and away from the pond. When this is complete I removed the boards and filled the hole left by the boards with more soil. This also has the advantage of making the pond 4 inches deeper and about 2 feet wider.