I've not used a completely enclosed 3-D silicone mold, but I have used some that are almost completely enclosed, and the soap takes longer to fully set up in silicone, with less surface area for the water to evaporate from.
You specific recipe impacts how quickly a soap will harden, no matter what mold you use, so yes, we need the recipe. A recipe that gels quickly would be more desirable than a recipe that takes several days to become hard. Also your method and how hot your batter was during the soapmaking process impact how quickly your soap firms up in the mold.
3D molds require secure closure (a strap around the outside of the mold, is one method) and needs to remain undisturbed for the duration of the soap firming up. If your mold is oven safe, perhaps CPOP would help, and if not, then perhaps you need to add insulation to encourage gel.