One of them being that you should always pour your silicone from one place and let it coat the piece being copied. Otherwise, there might be lines on the mold. Another tip is for DIY mold release ...

A release agent consisting of petroleum jelly ... [Eric] has also shown us how to make much larger silicone molds in the past. If you find yourself making lots of different-sized mold boxes ...

don't release the ice easily, take up too much space in the freezer, or produce misshapen cubes. To solve those problems, classic plastic trays are being replaced by silicone molds and trays with ...