What would you suggest to be the best way to get a good casting from molds that are detailed or have with little openings in the design? You have several options when using molds with holes or ones that are very detailed.  Options for molds that show holes in the casted piece. You cut them out with a craft knife (if you are using clay) before it is baked. It is easier to do this if you put it in the freezer for about 15 to 30 minutes first. This also helps cut down on fingerprints. Your casting will often look just as nice if the holes are left closed, but it depends on which mold you are using. Another option is to sand the back of the mold(flat side) after it is baked, until the holes through. You can do this by rubbing the flat side of the mold face-up over a sheet of sand-paper on a flat work surface. Options for molds that have very detailed edges. You cut them out with a craft knife as well, before it is baked. You can freeze first cut down on finger prints. Your casting will often look just as nice with the edges left on the casting, depending on which mold you are using. Another option is to sand the back of the mold(flat side) after it is baked, until the edges are sanded off. You can do this by rubbing the flat side of the mold face-up over a sheet of sand- paper on a flat work surface.