best way to clean slate tiles before using in terrarium?

Hi i found a source of free slate, its just scraps here and there so i plan to collect some for when i upgrade terrariums. I was just wondering how you all would go about cleaning them since they are scraps, and how long should they be left to dry before used in a terrarium.

My overall goal is to cover about 90% of the ground with slate and then maybe build some hides and a deck to lay on if i can gather enough, i plan on putting sand under it as an anchor and for heat displacement. I know sand is bad but im hoping it will just be small cracks between parts where i had to crack tiles. Also i have started feeding my little on meal worms from a bowl, he is still skeptical about the bowl but im hoping this will prevent any sand from being eaten.

If you have something similar going on please feel free to post pics or opinions on how you did it or would re do it. I guess i should say this will most likely be a 10 gallon tank maybe a 20.

For cleaning the slate tiles, I would scrub them well with hot water and a mild soap or dish detergent. After you've rinsed them, following with a disinfecting treatment of your choice (whatever you tend to use, bleach, ammonia, novalsan, etc.). Rinse thoroughly and either dry in the sun or put your oven on the lowest setting and dry in there.

Those suggestions sound great! I've heard of baking them in the oven as a great method for cleaning. I always wash and soak in Novalsan or bleach as well