Which design technique involves placing similar materials horizontally atop one another?

The technique referred to in the question is tracing and layering. This method involves arranging similar materials in a horizontal manner, creating a layered effect that emphasizes repetition and texture. Tracing and layering can provide depth and rhythm within a floral design, making it visually appealing and cohesive.

This technique helps to build a structured design where each layer can complement the others, allowing for a harmonious display that draws the eye. It is particularly effective in creating a sense of movement or flow in arrangements, as the layers can be varied in height or depth to enhance the visual interest without overwhelming the overall composition.