Here's a fantastic article that follows the process of developing a car concept from sketch to clay model. The designer is 23 year old Ross McSherry, who creates a 2+2 design for Alfa Romeo.

The attention to detail is amazing, with this car being designed around a Maserati Quattroporte steel monocoque, “allowing for Alfa Romeo to produce a luxury-sector vehicle for minimal initial expenditure.”

He’s even gone so far as to specify high tensile steel as the primary material for the body shells, and polypropylene bumpers to reduce weight and increase pedestrian safety.

[Source: Alfa Romeo Villa d'Este: design story]