Kitchen or anywhere DIY. Seems simple enough, depending on your gap between shelves, anywhere from ropes to ropes for your spacing. You could even use wider wood, just adjust your rope length to accommodate your width and height of your shelves.
Minimalist IKEA Cabinet Hack, and lots of other ideas on hiding a litter box. Not just for the litter box but for a dog's or cat's pet bed, when company is over or just during the day, just shut the door and it won't have to be seen until bedtime.