Custom robot chassis?

I have designed my own robot with my own drawn and designed chassis on papers. I have the design down but I am wondering how would I make my own chassis? Ik there are ones for sale online but they are too specific and my one is specific to my robotics design. What materials would I use and how would I shape and craft my own basic chassis instead of buying one?
Thanks.

Materials and techniques will depend on the design of the robot.

In the past, I've used CDs as a chassis, with PCB spacers between them, but for bot of more than a couple of hundred grams, they're useless.

What materials would I use

Ones that you have the tools to cut and form.

how would I shape and craft my own basic chassis

Using the materials and tools that you know how to use.

Not exactly rocket science, Einstein.