Model it in 3D

I used Lightwave 3D (an animation and modeling tool for visual effects) in the following image to create my prototype part. However, you can use Blender (free), Autocad, or any other modeling tool to create your virtual part for printing:

It's important to note that there are many ways to make your master for your mould. Clay modeling, wood carving, and even hot glue molding are among these methods. I prefer CAD and 3D printing as it's much more accurate, with a much more finished look.

Once it's done, it can be exported for 3D printing.