How were central floor panels called emblemata made and installed at Pompeii?

At Pompeii, central floor panels known as emblemata were typically crafted using a highly detailed technique called opus vermiculatum. This method utilized tiny tesserae—small cubes of stone, ceramic, or glass—to achieve fine color gradations and precise contours, effectively allowing artists to "paint in stone."12

Rather than being created directly on the floor, many of these high-quality panels appear to have been manufactured as ready-made pieces. Craftsmen would preset the intricate designs onto portable trays made of stone or terra-cotta. Once completed, these trays were embedded into the mortar of the floor. The surrounding area of the floor was then finished using the standard, direct method with coarser mosaic work, often referred to as opus tessellatum.132