Looks good so far.. When I had my one car garage built at my old house, I didn't plan good enough on the slab. It was poured too low, in one corner (yard sloped, but not as hard as yours). Over time, dirt got built up on the back side, and when we would get a really good rain, it would flood the whole garage with water and mud. So make sure you have a good drainage plan, or build your slab really high on that one side. Mine was a mess to deal with after a heavy rain.