Incubators for breeding leopard geckos can be expensive. Fortunately you can build your own. This will save you money, and the materials are easy to acquire online or through an ordinary pet store.
Fill the glass tank with sand until there is approximately one inch of sand all the way around. Smooth the sand out so that it is flat from one end to the other.
Place the plastic container in the middle of the sand, pressing it down so that it is held in place.
Attach the heating pad to the bottom or side of the tank. You want to make sure that the heating source is touching the sand, because the sand will be what maintains the heat inside the incubator tank. Another heating source such as a heating rock may suffice, but a heating pad will provide the most consistent temperature with the best amount of coverage.
Fill the plastic container halfway up with vermiculite. You want to make sure that the container is large enough to accommodate however many eggs you need to incubate, and deep enough that you can fit the eggs in comfortably.
Create an indentation in the vermiculite with your thumb for every egg, so that each has its own place. Make sure that the indentations are deep and wide enough to comfortably accommodate the eggs.
Drip water into the vermiculite in order to dampen it slightly. Place the eggs in the container carefully, taking care not to turn or flip them. If you rotate the eggs too much, you can cause damage to the growing embryos within them.
Place the lid on top of the container, and place the thermometer on the glass so that you can keep track of the temperature. A steady warmth with few fluctuations will give your leopard gecko eggs the best chance of survival. The ideal temperature is between 25 and 31.1 degrees Celsius.