This structure is made of Bloxes, what are bloxes I here you ask?"Bloxes are building blocks made of interlocking pieces of corrugated cardboard, folded together. Their unique shape and structure make them exceptionally strong and lightweight—you could build yourself a platform to stand on, and then pick it up and move it wherever you need to."
I am not promoting or endorsing these different products, they are just some examples of ways to do things with cardboard. There are many ways that do not need anything more than a slot cut into it and joined to another box.