We must design free hardware. But the question remains: how?
First, we must understand why we can't make hardware free the same way we make software free. Hardware and software are fundamentally different. A program, even in compiled executable form, is a collection of data which can be interpreted as instruction for a computer. Like any other digital work, it can be copied and changed using a computer. A copy of a program has no inherent physical form or embodiment.
By contrast, hardware is a physical structure and its physicality is crucial. While the hardware's design might be represented as data, in some cases even as a program, the design is not the hardware. A design for a CPU can't execute a program. You won't get very far trying to type on a design for a keyboard or display pixels on a design for a screen.
Furthermore, while you can use a computer to modify or copy the hardware design, a computer can't convert the design into the physical structure it describes. That requires fabrication equipment.