Hi Chichi. Are you the famous golfing Chichi? Anyhow for your shed I would just remove the organics around the perimeter of the shed. Lay down some crushed stone and dry lay your flat stone up to about 8" above grade. The sills sit directly on the stone. The wall sheathing should extend down past the sills a couple of inches to keep them dry. The shed will rise and fall every year but a timber shed will ride it out like a boat and will outlast us both. Cinder blocks laid on patio stones will do the trick also but don't look nearly as good.
