A decent design can change a slanting site into a great garden. I have deliberate many sloping parks; I like to do them but know how difficult they can be to get accurate. You need a full understanding of site structure and a complete plan to address the level changes in order to avoid the many difficulties of making gardens on slopes.
The best way to design grounds on sloping sites is to build terraces using spongy walls to provide flat areas that can be used as useful spaces within the garden. The level changes in a sloping garden command naturally the formation of outdoor rooms at different altitudes each with a unique atmosphere.
The spaces can be surrounded and/or sunken for privacy, opened up creating a sunny terrace with a fabulous view. You can also navigate www.springpot.com for slope gardening.
The steps and ramps needed to navigate and access the levels can provide different journeys around the garden as well as being sculptural design types.
The garden must be organized to create functional spaces that work with the level changes and meet the customers brief. In some places, retaining walls can be no more than 1m high touching the street or 1.8m high away in the garden without requiring planning consent.
It is hardly feasible or desirable to create one large retaining wall to reduce the garden to a single level. Other than on a very small slope this would be overbearing, make some portions of the garden hard to access, and almost certainly raise the garden so that it oversteps on neighbors privacy. Avoid very high retaining walls, and riven the garden into fewer, lower levels.