It all depends on soil conditions. Many use surface deckblock, it will heave (relatively even) with the frost - and then settle again to regular elevation, however, it CANNOT be anchored to your house then.
If you need/want to use footings, how close you can get to your pool is relative to the soil and conditions you are working in, if it's very sandy soil, it can cave at just about any time since it does not harden up when it dries, however, clay soil, once dry (mid summer) is very hard and you can cut into it vertically without risk of collapse.