Hello. When you have a clay sub grade, it is going to require a little more work. Proper drainage is key. If you are on a cross slope, you need to channel runoff around the pad. If you think you will ever pave it or build a structure on top of it in the future, then you need to do it right the 1st time. You first need to moisture condition and compact the clay subgrade. This is done by scarifying (plowing) the top 6" and adding water, and re-compacting. Then you need to import the crushed limestone road base. I would use a minimum of 8" - 12", placed and compacted in two or three 4" lifts. The base needs to be moisture conditioned as it is being place as well. Once the base is compacted in place, I used a top dressing of about 1" of pea gravel. This keeps the base from tracking and make a clean surface to drive/walk on.