Use Mold Star™ 15 to make the mold. It is mixed 1 part A to 1 part B by volume. Dispense part A and then dispense an equal part of B. Combine both parts A and B into a larger mixing container and mix thoroughly until there are no color streaks. Mold Star 15 has a pot life of 50 minutes. It does not need to be vacuum degassed.
Pour the rubber into the lowest part of the mold box in a long, thin stream in a single spot and let it rise over the model, finding its own level.