Measure the length you want to make the wall over the ground's surface. Hammer a stake into the ground at each end. Measure out from those two stakes the width of the stones you intend to use, then drive stakes into the ground in these locations to create a rectangle on the ground.
Dig a ditch in the rectangle created by the stakes. Dig to a depth of 12 inches on the lowest part or parts of the uneven land. As you move along the uneven land, dig the other areas down to level with the low parts to create a level base.
Fill the ditch 6 inches deep with gravel, then level the gravel. Cover the gravel with 1 inch of coarse sand; place a level at one end of the trench to make sure the sand sits evenly. Smooth the sand with a spade, or add sand to the ditch as needed until the sand is level.
Place the first row of stones along the leveled sand from one end of the trench to the other. Stack stones on top of the first row as evenly as possible until you fill the entire trench and create a wall that reaches the height you want.