Vallien is the most widely recognized and admired artist working in glass in Sweden. Like many Swedish studio artists, he has pursued a career designing for industry in addition to maintaining an independent practice. He is also a well-traveled teacher who has influenced an entire generation of artists working in glass in Europe and abroad. Sand casting—that is, pouring molten glass into a prepared bed of sand to create a form—is a technique that Vallien pioneered in the 1980s. He is best known for his sand-cast boats, such as Cargo Seed. These large boats, inspired by Viking boat burials, address the themes of journey, memory, and time. Elements of archaeology (re-creations of artifacts), water (palette), and states of consciousness, such as suspended animation (the immobilization of objects in glass), are also evident in this work.