Shed Foundation Drawing Plans

I am trying to buy a metal building an i need help with concrete the metal building will be 30x40x14 or 30x50x14 i need drawings for permit on the concrete pad. I am not sure if i need to pour a monolic pad or a step wall my issue is my driveway is on opposite side of yard in a low area i have bought clay to make my pad the same as my driveway it puts me 14inchs low on one end an about 6 inchs on other end and i think code in my area says my footing needs to be 12inch below undisturbed soil for frost line. Building requires 12x12 footing with 2 pieces of rebar running the whole way