You can certainly do this with any silicone mold, and the hot glue hold ... Heat up the hot glue gun and load the desired glue stick. Slowly use the gun to fill a gem mold with layers of glue.

Sugru is a moldable glue. It looks like Play-Doh, can be shaped around any object, sticks to almost any material, is waterproof, heat-resistant and dries to a silicone rubbery finish in 24 hours.

[Print Practical] thought it just might be possible to 3D print custom molds at home and do it himself. His first attempt didn’t go so well. As it turns out, hot glue likes to stick to things ...

The project started with a set of 3D-printed tire molds that bolt to the standard wheels. A bot of melted glue sticks is poured into the mold, allowed to cool, and the mold sections are removed ...