Box Designer is a little app that can generate the outlines for a box to be out of some material with a cutting device (ideally using wood/acrylic on a lasercutter!). You tell it the dimensions of the box (width, height, depth, material width), and it generates a PDF with the outlines for the 6 sides of the box. The dimensions are the outside lengths of the box.
The edges are notched, so the faces of the box snaps together well. You can import the PDF file that Box Designer creates into CorelDraw (or any other standard CAD program) and manipulate it further there. You probably want to rearrange the faces to fit on the material you have at hand.
The code for the underlying rendering engine is up on GitHub.