Depending on the amount of tunnels wanted, two 10 pound bags of excavator clay may be suitable for a 40 gallon tank. it is recommended to set up your leopard gecko in a temporary tank until the excavator is completely dry. A heat lamp may be placed over the excavator to help it dry faster.
To change the shape of the substrate or remove it, remove all reptiles from your terrarium. Then mist the substrate with water to soften it enough to mold or remove.
The dry time of the excavator clay depends on how much water was used and how thick a layer of excavator is placed. To speed up the dry time you can always put a fan or a heat lamp over the tank to help.