One gent I know sometimes turns a rough softwood bowl made of a 2x glue up and sized so the outside of the "open" bowl drops in. Then he does the same to make a plug that fits in it to take up the inside volume. When ready he puts the resin in and then puts it in a large pressure pot and pressurizes it as high as the pot is rated for. You need extra resin to allow for what finds new crevices so the plug and outer bowl are taller than the cast one. When cured he mounts the works and turns off the molds revealing the creation inside. Because it is a time consuming process he now usually casts the resin into the wood block first and then cores the middle out for more bowls and bandsaws the corners off to use for smaller turnings. An alternative is to find cheap plastic bowls to use instead.
Pete
