Box Designer (Connectionlab) - In this on-line application you can enter the desired dimensions of your box and then create a pdf. Keep in mind that you adjust your "material thickness" to the thickness of the material you are going to use.
You have to edit the. pdf by importing it in Inkscape – the black lines must be converted to red (RGB 255, 0.1 mm thick).
After you have done this, you should group the blocks so that you can put them on one or more sheets if needed.