The first mold is basically a slab with a hole in the shape of an object. This object could be whatever you want it to be. I chose to make the first mold in the shape of a g-clef. I used both Fusion 360 and Inkscape to make this mold. For this method, I found a tutorial on YouTube by LazerLord10 (https://www.youtube.com/watch?v=s0stI95C5Pc). To make this mold, use the following steps:
Open fusion 360 and start a new design.
Go to create -> box
Create a box that is 80mm by 80mm. For the height, go with 10mm.