Build a basic concrete block wall. Outline the courtyard area with stakes and mason's twine. Square the corners with 3-4-5 measurements. Measure with a tape measure 3 feet down one wall, 4 feet down another and connect the ends in a triangle; if that diagonal line is 5 feet, the corner is square. Mark all walls.
Dig a trench with a shovel for concrete footings, twice as wide and a third as high as the wall. For a typical block wall 6 feet high, the trench would be 16 inches-by-2 feet. Place a layer of compacted gravel in the bottom of the trench, and install 1/2-inch steel reinforcing bar (rebar) vertically at all corners and every 4 feet in between. Sink the rebar into the ground to the finished height of the wall.
Pour concrete into the trench. Mix it in a wheelbarrow using a prepared mix or hire a concrete supplier. Fill the trench to ground level and smooth the top with a rectangular mason's trowel. Let the concrete cure 72 hours.
Lay a first course of blocks in a 1/2-inch thick bed of mortar on the footing. Use blocks with full ends and set blocks firmly into the mortar but without any mortar between ends; butt ends tightly together. Make sure the block tops are level the entire length of the wall, using a spirit level and the string guideline to keep blocks straight. Lay a base course of blocks on all courtyard walls.
Add other courses, stacking blocks tightly together without mortar and overlapping blocks at corners. Place blocks over the rebar at those points, with the rebar in the holes in the blocks. Stack blocks to the desired height. Fill rebar joints with concrete grout, let that cure and add 2-inch or 4-inch solid blocks on top as a cap. Seal the walls with a 1/8-inch thick layer of surface bonding cement on both sides of the wall to secure the blocks.
Spread a base or scratch coat of stucco over both sides of all walls, 3/8-inch thick, using the rectangular trowel. Scratch horizontal lines in it with the notched edge of the trowel, a broom or a leaf rake. Let that cure 72 hours and add a second or brown coat 3/8-inch thick. Smooth this coat with a long board pulled down the wall from top to bottom; remove excess material at the bottom. Let that cure 24 hours.
Finish the stucco courtyard with a final coat of stucco, 1/8-inch thick. Smooth this with the trowel or apply a texture. Make swirls or part-circles with the notched edge of the trowel, or give it a stippled or popcorn surface by pulling stucco up with the flat bottom of the trowel, then smoothing those peaks with the flat edge. Let this coat cure 24 hours.