An engineered stone production plant includes a vacuum vibration press (VVP) suspended above the ground, so that a conveyor belt and/or returning empty trays or molds from a curing oven to a mixing station can pass beneath the VVP. Rigid, self-supporting trays or molds can convey slabs through the plant on rollers, which allow independent horizontal movement of the slabs during spreading and coloring/veining of the slab mixture. Embodiments include air levitation for transporting slabs into and out of the VVP. The curing oven can be air-heated. The pressing plate can be sealed with the tray ormold by walls that extend downwardly from the press plate over a flexible covering sheet, by a gasket surrounding the pressing plate, or by an angle strip surrounding the slab mixture. In embodiments, the slab size can be changed by exchanging elastomeric mold walls, or by exchanging molds and pressing platens.