1) Prepare a toy you’ll cast. I used 3-inch penguin toy.
2) Make a hole on top of it to make a poring gate. And make a tiny hole on the bottom to make vents so that excess resin and bubbles can go out of the mold.
3) Build the mold box around the object using one large piece of foamcore. (Becareful! If you make the mold too thick, you’ll waste silicone and the part will be harder to cut out. And if you make it too thin, the silicone can deform under the poured resin later)
4) Place the toy about one-inch above the bottom.