Resin casting lets you produce parts that would be otherwise ... you’ll cast the mating silicone mold on top. There are two methods I employed. My usual is to use light glues like rubber cement ...

[Jan] notes that this generally necessitates the use of condensation-cure silicones, as additive types don’t cure well in resin molds. The condensation silicone is mixed up, degassed, and poured ...