Paper (thick, about 160 g / m² or 5.5oz / m²), Scissors, Glue, Ruler
To make your work easier, I recommend using a cutter, tweezers, those little pins, and tiny scissors used for cutting out silhouettes.
You can find the instructions here: http://www.kamibox.de/download
Please download the PDF and print at least the second page. Ink is expensive. On that kind of paper, that is twice as thick and heavy as normal paper, the printer options for non-glossy photo paper are usually the best.