How do you make custom tracks?

You don't. You don't make custom tracks.

You shouldn't bother.

Or you get someone else to do it for you.

Or you get someone else to do it for you.

I was just curious. It seems like it would be hard to do. For now I'll take your advice.

To be very honest, I've seen many people start making ct's and give up on them halfway through, having done hours of work for nothing. Plus, if you do finish them, they'll often end up being glitchy and crashing the game. I wouldn't recommend anyone building a CT because of that.