My process is as follows
1) make a tiny version of the shape with clay. Then cut it out and flatten it.
2) Measure the space I want to fill.
3) Scale it up. You can do this by scanning it into a computer and printing it. My software wasnt working so I just copied the shape using measurements.
Sometimes this method helps without any math, just seeing the shape flattened can help you get a better handle on how to get the shapes your after.