Designing the layout of a chemical plant is a complex and important task. Its main objective is to find a most economical spatial arrangement of the equipment and associated pipes that satisfies construction, operation, maintenance and safety constraints. The problem is so complex it is still solved manually, taking multiple engineers many months (or even years) to complete. This paper provides (a) the most comprehensive model ever reported in the literature for spatially arranging the equipment, and (b) a Large Neighbourhood Search framework that enables complete solvers explore much larger neighbourhoods than previous approaches to this problem. The two contributions are part of a system being developed in collaboration with Woodside Energy Ltd. for arranging their Liquefied Natural Gas plants. The results are indeed so promising that Woodside are actively exploring its commercialisation.