Step 1: Basic plans
The entire structure is designed to accommodate the size of a golf ball. The plan I laid out uses two 49" by 97" sheets of MDF (one 1/2" thick and the other 3/4").
I also used some 1/4" MDF, a few pieces of PVC, an old plastic mudflap, a piece of used plexiglass, and a handful of other little things.
These photos are of the plans that I sketched out. Many things changed as the project progressed, but you can get an idea where it all started.