Complex sentence: In this method modular concrete elements (i.e. walls, columns, structural supports, etc.) are formed on a concrete slab; usually the building floor, but sometimes a temporary concrete casting surface near the building footprint.
Split into simpler sentences: In this method modular concrete elements (i.e. walls, columns, structural supports, etc.) are formed. These elements are often formed on a concrete slab that is the building floor, or a temporary concrete casting surface near the building footprint.