I used Flexwax to create a composite wax mold from a old glass liquor bottle my grandmother gave me. I heated up the wax, then brushed it onto the glass. After I had built up a sizable layer, I wrapped cheesecloth around the wax to strengthen the mold. I then reapplied another layer of wax. I repeated this process twice.
After the composite mold hardened, I cut it open down the side and removed the glass bottle. I then took a coat hanger and bent it into a stand so I could pour the Hydrostone into the mold. After the mold was poured, I cut open the wax mold (again) to remove the final Hydrostone cast.