Pond construction can be time consuming and costly and not as simple as one might think. There are so many ways to build a pond as there are pond designs, so you need to choose a method that works for your budget and lifestyle. To build a pond, start from the bottom. First you dig a hole, then place the base.
Concrete trim is the most expensive in stone (literally) method available. While it is resistant to all forms of stress and decay, building it can be messy. When handling concrete, take precautionary measures because once it is dry, do not back any back. You can have concrete delivered or buy ready-mixed concrete where all we do is add water and mild in your digging area. A greater benefit to the concrete use is the little maintenance that it requires. If there is a hole or a weak spot you can fill in the problem area more concrete.
Another option is to use what is known as a membrane liner. These sheets of tight fabric fibers resistant to water leaks are fixed to the floor. Obviously the thicker you buy the less likely you will have water to penetrate the soil. The liners are placed in the pond cavity and screwed to the floor. The key is to make sure there are no holes where the water will be. Liners are the least expensive techniques for pond construction. And a great plus is the ease of replacement or design modification.
Prefabricated or molded, fiberglass
The easiest way to establish a base for your pond is to buy a molded premade of a fiberglass resin. The problem with this is that they do not last long. It deteriorates faster than any other method of pond construction.