One of the most important elements in creating realistic sound effects is to have a good understanding of the source material. When it comes to creating bone-breaking and crushing sound effects, it's important to have a good grasp of what bones actually sound like when they break.
There are a few ways to go about this, but one of the easiest is to simply recording the sound of breaking bones using a microphone. Once you have a good recording of breaking bones, the next step is to begin experimenting with different vegetables and fruits to see what kinds of sounds they can produce.
For example, carrots are great for creating bone-crushing sound effects. Simply take a carrot and break it in half, then record the sound it makes with a microphone. You can also experiment with different fruits and vegetables to see what kinds of unique sounds they can create.
Once you have a collection of different sounds, the next step is to begin creating your sound design. This is where you'll take the raw recordings of breaking bones and crushing vegetables and begin to manipulate them to create the desired effect.
For example, you can use EQ to shape the sound of the bone breaking, or you can use a compressor to make the sound more impactful. You can also add reverb to create a more realistic environment, or delay to create an echoey effect. The possibilities are endless, so experiment with different effects and see what sounds you can create!