Depending on how the land is sloped, and where your property lines are relative to the contours, with a steep slope, I always imagine a series of terraces, swales and relatively level winding walkways, with flat landings, that support retention/irrigation ponds, hugalkultural mound gardens, and/or open groves.
Different terrace layers and retaining walls can be designed and tamped to drain or hold water in the appropriate places, minimizing erosion.
In an ideal finalized situation, trees and stone would hold the hill in place. Trees keep the soil from moving, and the stones slow water runoff by supporting shrubs and preventing gullies.
Immediately logs and hay bales can temporarily fill-in for support trees while the roots of said trees establish themselves.
With a blank canvas like you described, I'd start with the swales and access trails, setting up the tamped water holding wetland like terrace layers, and blocking gullies at the top, so that water flows through that system, and support the ground on the flat level pathways above and below the swales. On the slopes in between, I would plant the fruit/nut trees and understory perennials, biennials and shrubs in relevant species specific, and landscape relevant sites. With this set-up you will need a good deal of biodiversity for the site to support itself.
For the slopes in between the swales and walkways, Trees and shrubs with deep strong roots, as well as ones with shallow roots that drink a lot of water, at strategic and relevant locations. Eventually Set some stones, or build plant supported stone walls in between the hillside holding trees, to fill in any remaining gaps in slope stability or water flow.
Good luck!
