Dealing with a slope can be tough, especially if you don't have the budget to hire people to put in a retaining wall. Depending on the scale of the grade change, it may be worth trying to do it yourself. It's hard work moving stones around so don't say I didn't warn you.😄💪Ideally what you would have is gravel behind the wall, to allow for proper drainage. And you need to dig into the ground to place the larger stones firmly in place, so the others can get wedged against them so they don’t roll