I started by using 1/2 inch thick acrylic.

This 18 inch by 24 inch sheet has sharp corners, so I wanted to soften it a bit. I started by using a one gallon paint can as a template and marked the corners for rounding.

I cut these corners using a sabre saw, moving slowly.

This was followed by cutting out slots for the wheels. I drilled starter holes, then used the sabre saw to cut out the rectangles where the wheels would fit.