This is the reverse mold of the object in the previous picture, done using a two-part silicone rubber mold kit you can get online or at a local art store. You mix the two things in the bottles in a 5:1 ratio, and then pour it over the object to be cast. Here you can see I've dug out the clay for the light, so that the mold material filled that hole in. Now, when I pour the resin, it won't fill up the space where the hole needs to be. Still with me?