I'm in the process of laying a patio. The patio is only 2.4m x 2.4m so not too big and a relatively simple job. I've dug out 150mm to allow 80mm of hardcore, 40mm of sand and cement and 30mm for the paving slabs. Now the problem I have is that the ground isn't level. I've put some pegs in and measured, and simply put, the ground on the left hand side is approx 90mm higher than the ground on the right hand side (so a 90mm drop). I'm allowing for a 30mm drop to go from left to right. So, if I start at the highest side, by the time I get to the lowest side, the patio will be around 60mm higher than the ground. If I start at the lowest side, by the time I get to the highest side, the ground will be 60mm higher than the patio. Do I need some edging stone or something similar? Or could I get away without. Or alternatively could I do a steeper drop so the difference isn't as much, say 60mm drop instead? In which case the difference will only be 30mm on either side (depending on which side I start). It will only be used for light traffic, few chairs and sitting out and enjoying the sun. Any help would be appreciated.