Locate your patio flowerbed where you have 24 inches in depth and at least 32 inches in width to work with at the edge of the patio so that the raised bed is located over soil.
Lay out two parallel lines of cinder blocks, with the holes facing up and 1/2 inch of space between them. Place one cinder block on each end in between, and perpendicular to, the two rows of cinder blocks. Decide if this garden is the appropriate size before continuing. When you're ready to start, move the cinder blocks out of the way.
Place mortar in the wheelbarrow, and add water slowly. Mix the mortar with the shovel until it's thoroughly dampened and is the consistency of raw hamburger.
Place the first cinder block in position. Butter the interior end of the cinder block with mortar using a trowel, and place the second cinder block tightly against the mortar. Tap the far end of the cinder block with the butt end of the trowel handle several times to set it against the mortar. Continue in this manner until you have buttered and placed all of your cinder blocks.
Allow the flowerbed to dry overnight, and fill it with potting soil.