I was inspired by Michael Kröhnert's cool chitboxes for the game Shipyard to write a generator that can make similar boxes for any game. He was nice enough to give me permission to publish the generator here and provide his great instructions.
Sorry, the image is of a quick paper mockup I made.
These are copied from Michael Kröhnert's pdf for the game Shipyard - please find the more scalable pdf version there.
The generator will always scale images to fill the sides of the box. For best quality output, I recommend using images that actually have the right dimensions (width x length for the main image and width x height for the side image).
Does it actually make sense to use a different width and length? Yes, it does in the sense that you can produce rectangular boxes that way, and the folding will still work. However, in this case the side image will get scaled to two different aspect ratios (width x height as well as length x height - you could just leave it blank or use a uniform colour image if this bugs you) and there will be no cutting/folding guides because I haven't had time to do the math to figure out where they go in this case. I may do a version that takes two different side images to address the former problem at some point.
This generator produces both the 100% scale version for the lid and the 95% scale version of the same image for the bottom of the box on two separate pages. Print both pages on thick paper (100lb index paper, about 200 g/m^2) and follow these folding/cutting instructions: