When I built my first Maslow CNC frame, I didn’t have much carpentry experience, and I didn’t realize how warped 2x4s and lumber-yard plywood could be. My 3/4 AC plywood waste-board turned out pretty warped. This is good enough for many projects, but now that I have an improved Z-axis stage, I want to try building giant printed circuit boards (PCBs) by carving 1/8 inch (3.2 mm) copper-clad laminate. [yes, yes, I know breathing fiberglass dust is hazardous!]
What are the best methods and available (and affordable) materials for making a highly planar waste-board/frame? Is MDF a good candidate? Are 2x4s hopeless?