The rules of resin casting are simple. Mix 3% of hardener into your resin (i.e. the hardener should be calculated to 3% of the weight of your resin), this can be measured with a scale.
If too much hardener goes into the resin, it may crack. This is sometimes done intentionally by artists. If you go way over 3%, it starts to smoke. Too little resin, and it might not harden. The quantity of hardener is key to producing a good result.
Afterwards, you can pour the resin into the mould. Items can be cast in the resin, but be warned that it tends to ‘cook’. One could also opt to poke out the bubbles with a needle to produce a cleaner finish.
When the resin is cured, we can pop the resin out of the mould, and it should retain a solid shape.