How can I effectively build a retaining wall on a slope?

To effectively build a retaining wall on a slope, you should first plan the wall's design and layout. Then, prepare the site by leveling the ground and digging a trench for the base. Install a sturdy base layer, such as gravel or crushed stone, and compact it well. Place the first row of blocks or stones, ensuring they are level and backfilled with gravel. Continue stacking the blocks, adding drainage behind the wall, and backfilling as you go. Finally, cap the wall with a finishing layer for stability and aesthetics.