Lay the pond liner on the ground, upside down, in the desired location for the garden pond. A pond works best on fairly level ground in an area that receives morning sunshine and afternoon shade. Keep the pond away from trees if you want to reduce your fall pond maintenance and spend less time cleaning out leaves from the pond.
Spray the edges around the pond liner with landscaping spray paint about 2 inches out from the liner edges.
Dig out a hole within the spray painted area to match the dimensions of the pond liner, making the hole about 2 inches wider and deeper than the pond liner. Use basic hand digging tools, such as a round-point shovel, spade and mattock to dig the hole. Dig out any rocks, roots or similar hard objects that could puncture the liner. Replace the void left from their removal with clean fill dirt.
Line the hole with about 2 inches of wet, coarse sand. Pack the sides and bottom of the hole as tightly as possible, using your feet or a hand tamper. Instead of purchasing a hand tamper specifically for this project, try screwing a flat board to the bottom of a longer board. Spray the soil and sand lightly with water to make it easier to pack.
Place the shell in the hole and check to ensure the lip is raised about 1 inch above soil grade. Additionally, lay a two-by-four across the pond and set a carpenter's level on the board to check for level. Add or remove soil as needed to make the pond level and ensure the lip sits 1 inch above grade. Place the shell back in the hole after making the adjustments.
Fill the pond with water. Backfill the empty spaces between the pond liner and soil as you fill the pond. The extra space you left when digging the hole must be filled in with soil to prevent the liner from cracking. Push soil in around the edges and pack it with the handle of a shovel or a thin board. Only backfill up to the current water level because the pressure from the water inside the liner makes it easier to pack the soil.
Add rocks, plants and other decorative elements around the filled pond, as desired. You can place rocks on the pond liner to conceal the 1-inch raised lip, but they should only overhand the pond lip by an inch or two. Do not add rocks inside the pond liner because they can puncture the hard plastic and create places for dirt, leaves and unwanted pond creatures to hide.