The back of my house slopes down and away about 20 ft. My brickies have put up a nice solid 5 ft retaining wall and now I need to back fill the space left to get the base level for some paving slabs. There are existing slabs from the old patio still in place and a concrete section where an old shed stood. What is the procedure for filling in such a large area (20 ft by 20ft approx) I have tons of clay ,half bricks general rubble sitting around in the garden. Can i mix it all up compact it with whacker then finish with mot 1 and dry mix?