I grow mine on the ground and just put straw on top, adding more as the plants get taller. I don't till my garden at all and have permanent beds with permanent mulch, so the ground is pretty loose. I do make a shallow (1") trench just so the pieces of potato stay put. Usually this works very well and I can pick out most of the potatoes without any digging. This year, however was a totally different story and the results were poor because of the heat and dry weather.