I have seen a lot of good advice on adding gravel/sand to the tray to help with the thermal mass of the oven. However I am unclear on one thing (and I'll apologize in advance if this is dumb!) Does this mean add it and also add water or is there no need for water in that pan? I ask because I thought completely removing moisture might not be a good thing but I don't see anything mentioning anything other than sand/gravel. Just a little unclear. Can someone let me know? Thanks!!!