We did it a little differently to make the harvesting of potatoes easier. We build an 18 by 18 in. frame and SCREWED planks on each side. As the vines will grow we will add planks and soil. And if we want to harvest potatoes from the bottom we will just unscrew the planks, take the potaoes we want and put back the planks. Supposedly you can grow 100 lbs of potatoes in an 18x18 wide, 30 in. high box. I hope it works well!
So easy a toddler can do it :)