Dig a 6-inch-deep trench equal to the width of the first terrace step. You will need to bury the first timber halfway to anchor it into the ground.
Dig trenches into the hillside perpendicular to the face of the slope. These trenches are for the side timbers of the terrace and should only be one inch longer than the width of the timbers.
Cut two timbers to length to fit into the side trenches using a chain saw.
Arrange the timbers into the trenches and drill holes every 18 inches using the power drill.
Secure the timbers in place by pounding reinforcing bars through the holes with a sledgehammer. These anchors should penetrate at least 12 inches below the timbers into the soil.
Place another timber over the back edge of the current terrace to create the front face of the next step up the hill. Overlap the anchor holes in the corner of the new timber with the back corners on the side timbers from the lower level. This will lock the tiers in place and add stability to the terrace.
Repeat steps 1 through 6 until your terrace is at the desired height.
Fill the terrace levels with topsoil to create level tiers.