In my case, I built a 10'x12' shed on a slope in my back yard.
About 4' of the front (door side) is on level ground on pier blocks croncreted in.In the back I used 10" Kolumn Forms or sonic tubes.
At the steepest part I have about 3 1/2' of exposed form.
I used three rows, the two outer rows at 8' o/c and one row at 4' o/c between the outer rows. From front to back the forms are 4' o/c.
4"x6"x12' P.T. beams were used. The floor joists are 4"x6"x10'16" o/c
The rest is up to you. I built mine about 3 years ago, I use it for my lawn and garden tools and my Kawasaki Mule