There are two ways to set out foundation on a steep slope :-
1. Cut and fill refers to the process of leveling out the ground for the foundation by adding soil, removing it, or both. Soil may be brought in to fill the plot and make it level, or it can be dug (cut) from the slope and either trucked out or used to shore up retaining walls for the home. Depending on the grade, soil conditions, and other factors, cutting and filling can make construction multiple time more expensive than that for a home on a flat site.
2. Using stilts is an alternative to cutting into the slope that involves using a crane to lift the home onto supporting wood or steel columns. This can be a much more cost-effective method than cut and fill and can also open up the realm of possibilities for home replacement such as building out water over trees or water.