That would work if the ground/site is fairly close to level. You just dig some shallow trenches, fill with gravel, and put the skids on top. If the ground is not level, you’ll need to do something else. The plans I got from icreatables included various foundation plans for such situations.
FWIW, my small yard is close to level so I used two 6x6s. After laying them parallel, I placed a STRAIGHT 2×4 across the skids in various places and directions, and used a long spirit level to see where I need to add more gravel, dirt, etc.