It's real easy. You just use a substrate which is diggable/burrowable, and allows adequate air circulation, do not use something such as clay which doesn't allow much breathing. A female would not choose to lay in something that her eggs would not be able to breathe in. Fill the entire enclosure with the substrate, to a suitable depth. I would say at least 10-12" at minimum, some people choose to go much deeper than that, for monitors will be burrowing much deeper than that in nature. Make sure that there are areas at the bottom of the substrate which would be favorable to her laying, probably around 85-88F, but you should also give cooler and warmer areas for them to burrow into ato achieve proper temps for their own thermoregulation and comfort. This is the technique I am currently using with my odatria, and it appears to be working out pretty good for me so far, now that I am starting to learn what some of my animals' behaviors and patterns really mean.
I wish you the best of luck with your ackies, they sure are a blast, and what a joy it would be for you to hatch out some babies of your own.. Take care, have a great day!
BOb

The Odatriad