In the process of digging foundations for a 4x4 log cabin. I've dug an area 100mm larger than the cabin all round. With the slope of the land, one side of the hardcore is going to be around 80mm higher than ground level. For the purpose of putting the type 1 down I've put a length of 3x2 down to effectively box the type 1 in and give me a level to work to. Should I just leave the 3x2 in and fill behind the timber with soil or remove the timber and fill with soil? Thanks.