Leveling site for pre-fab shed

I need an economical solution to leveling a site for the install of a "Tuff Shed" . My thought was to construct a floor/deck frame using pre-cast piers and 4x4 pressure treated lumber. THe shed comes with a 6 " galvanized joist system and would be set on top (12 x 16 ft hed). Also thought of sing a gravel pad. We have a slope that I'll need to compensate for (about 12"). Any input appreciated.