A Yorba Linda pad was made by a grader, cut on the uphill side and filled on the downhill side, and the fill is the softer half. A patio poured to the back edge sits on fill, and that edge drops.
The hillside tracts, from the 1970s streets off Yorba Linda Boulevard to Bryant Ranch and East Lake Village in the 1980s and 1990s, were graded the same way, and each pad carries a drainage plan that sends water to the street and never over the slope, because water over a fill slope is how a slope fails. The original rear patios were poured 3 inches thick and pitched toward the slope because that felt right, and they have dropped at the back edge and sent decades of runoff down the fill.
So a slab here is built to the pad and not to the eye. The fill under the back edge is probed and dug to firm material, 4 inches of base is compacted, and steel runs through the slab so the panel spans the soft ground rather than settling into it. The pitch is set to a drain at the low corner that runs to the street under the side yard, the slab stops short of the top of slope by the setback the hillside rules give, and a wall at the edge is footed below the fill and drained.