I picked up some bulk Composimold on Amazon the other day. So far, seem impressive. As much as I like silicone for molding parts, it’s expensive. Composimold is about the same price but is re-usable. You toss it in a microwave safe bowl, nuke it, and pour it. Then you clean it up, nuke it, and re-used it. Pretty sweet!
I also got to test out my Lego box. Seems to work great. I tossed some plastilina on the bottom to hold it to my glass plate. I used the glass out of an old picture frame as my work area.