Just completed a test, set out a 4 x 4 grid pattern with wood, stand in middle of square, raise it to desired height. Do this by standing in middle of the box and looking down. Then face the gap and raise that. Its pretty quick and you get lovely straight raised ground walls. If you are starting on a very uneven surface, dig down a little, flatten, then raise it up. I built an 80m diameter circular fort and wish now that I had dug it all down first, and then built up, would have been faster.