Sink your mold halfway into modeling clay, then build a mold box around the area you want to pour, place your keys. Measure your silicone, mix, then pour the first half. Wait 24 hrs, then demold, clean up any overpours then place jig in silicone mold from the day before and repour the other half. If you write down the amount you used for the first half you can eliminate that step and just pour.