People planting in hard clay soils have to worry about "bathtub effect": drowning in a water-filled barely slow-draining container. If the plant survives the poor drainage, the roots may circle as though in a container. Our extremely sandy soils are nothing like that.
Most persons not on a tight budget, nor needing to stay within a reasonable quote, will want to dig a hole not quite as deep as the rootball, but far wider, and amend the native soil with long-lasting ingredients and non-NPK fertilizers for the deeper portion of the hole, and compost with native soil only near the top.
I recommend adding, into the native soil going back into the hole, Calcium sulfate (gypsum) for acid-pH- or neutral-adapted species, or agricultural lime or dolomite lime or basic slag for more alkaline-adapted species. Even for species that like mildly acidic soils, some alkaline calcium sources could be placed at the bottom of the hole. Acidic water moving down will slowly dissolve them.
Long-lasting soil amendments include charcoal, fossil humus (Humate powder), clay, phosphatic clay, rock phosphate, limestone gravel, rock dusts, diatomaceous earth, green sand, and worm castings.
Mix organic matter into the surface three inches of so out some three feet or more beyond the root ball. Make a berm of native soil around the outside of the rootball to hold hose waterings. Add fertilizer on planting day outside the berm--- when roots spread out there in a few weeks, they should find wonderful fertility. There should soon be lots of feeder roots several feet beyond the dripline.