According to Martha Stewart, quoted in the post directly below this one, you’re supposed to lay out your succulents in a triangle.
What I remembered is her cacti and succulent garden for its size, plant diversity and very personal design. To provide good drainage, a must-have for cacti, Sandy built a semicircle mound, added several large, attractive and locally purchased rocks to help keep the soil in place, and with little previous knowledge of cacti varieties, set out to collect the plants that would be set into the garden alongside the indoor-grown cacti from her previous home in Brooklyn, N.Y.
Oh no! They went with a Semicircle!