Using the given hardware (1/4″ diameter stock) you will be creating a chassis and wheel base(s).
They can be wheelsets, free spinning wheels, casters, or any combination of them. You can add steering if you’d like. The chassis does not need to move under it’s own power, but have a plan for it to be propelled.
Your design should be well crafted (precision and accuracy counts here), the chassis should be rigid and stable, the axels/bushings/wheels should be securely fastened.