How to design shape and depth
With a metric string draw the perimeter of the pond; consider that an oval shape makes it easier to position the fabric. In the center, expect a deeper area (40-60 cm) to prevent water from freezing in winter and to get too hot in summer, while around 20-30 cm depth.
Once you've chosen the location and defined its shape and size, it's time to start giving life to your pond.
Begin to dig from the perimeter. If you want to create a "ladder" pond, remember that the width of the steps must be at least 30 cm, so you can place vases of aquatic plants on the edges. The earth of the excavation can be reused to build a
little hill from which to start a small waterfall. Check that the excavated hole is "bubble". Once the excavation work is finished, clear the ground with stones, roots or other impurities and make the ground as uniform as possible.