3D Model Design for a 3D Printed Cube Frame

I want to make a mirrored infinite box, so I need the frame of a cube designed, so I can slide mirrored panels into each side to form a closed cube. The size is 20cm x 20cm. I have a general idea of what I want my design to include but am looking for input from a 3D designer to help with specific details and I am open to creative input. Someone with an engineering background or skilled in maths would help. I am aiming to have the final product printed in plastic or metal.