The construction process is pretty simple. Wood boxes were custom built with evenly spaced rope sized holes drilled through the top and bottom. Pre cut sections of rope were strung through the top and tied off at the bottom, allowing for the interior knot to hold the rope in place and taut. Just screw close the open side of the box and all those ugly knots are hidden away.
With this design the overall costs are kept pretty low for such a big impact. Rope is cheap, especially when bought in bulk, and wood boxes are very low cost to build. The true cost is going to be labor and time – it’s just a tedious and super repetitive process (source).