HCA: Hermit Crab Association

I have this half-log that's genuine wood and I saw that some small fuzzy, gray mold was growing on the underside. A lot of my crabs sleep under it together and I didn't want to expose them to constant mold. Is there a non-chemical way to safely clean and disinfect the mold? My current attempt is to put it in a ziploc bag and hang it by my window for a few days and hope the sunlight and dry bag can kill the mold.

Mold is not harmful to crabs, you just remove it when you see it. With the heat and humidity, it is bound to happen in most of our tanks at some point.
Your baggie method isn't going to work, unfortunately. You will want to scrub off the mold with water and a brush. Then boil or soak it in salt water, and allow it to dry (in the sun if you have any at this time of year) before putting it back in the tank.