Final answer:
The use of plaster is the traditional and most common practice for creating ornate moldings, which are elaborate decorative elements in architecture.
Step-by-step explanation:
The most common practice for making ornate moldings is the use of plaster. Moldings are decorative elements typically found on ceilings, walls, and frames, noted for their intricate designs and patterns. They can be created using a variety of materials, however, one of the traditional and still prevalent methods involves casting plaster into molds.
While materials like Foamcore, wood, and synthetics are also used, especially in modern construction for ease and cost-efficiency, none of the options provided (Foamcore, Fillet, V-grooves, Matting) is commonly associated with the crafting of ornate moldings.