Do not try this at home! It is silly, impractical, and inefficient... but fun
I started with the base octagon and for some unknown reason in a RHD rail system, the outside rails run counter-clockwise. There are two horizontal and two vertical loading/unloading lines that turn left into the octagon, and then turn left to exit; chain signals are used to prevent trains from blocking the entrance/exit lines, and train limits are used to ensure there is room to park for any train that heads into the octo. On the west side, there is a tiny siding for the fuel train to deliver fuel to this octo; on the east is a siding for my personal transport.
I then added the wave: a second lane running west to east under the octo, and east to west over the octo, as well as running north to south on the west side, and south to north on the east side. I tucked in connectors to allow trains to enter the octo from the wave, and exit back on to the wave. An empty octo looks like this: Next for another unknown reason, rather than stacking the octos in a straight line, I offset them, so that they touch on the diagonal corners. The intersections are
Anyway, here is my mini octo wave after about 200 rocket launches. Yes, the Factory Must Grow, and no, really, you do not want the BP... enjoy!