Like Ironflight said, there is a lot of cutting before splitting it in two.
The rough cutting to remove the excess material is good training and experimentation with cutting techniques.
I ended up with using the vans supplied cutting disc, but you need a good mandrel to avoid imbalance and wobbling. A wobbly tool makes things much harder.
Here is how I started (after getting new tools and mandrel, the first time didn’t go to well.....) https://youtu.be/DP7oAZ1zOi8
Make sure the cut off pieces are supported with your hand or tape to avoid seizing the cutting disc or worst case starting a crack.
I also made sure to sand all edges after each cutting session before I carried the bubble around.