Motzfeldt is best known for her glass creations. Her work is on show at the National Museum of Art, Architecture, and Design in Oslo, the Victoria and Albert Museum in London, the Kunstindustrimuseum in Copenhagen, the Nationalmuseum in Stockholm, and the Frauenau Glass Museum in Germany (donation Wolfgang Kermer).
Murano glassware was historically decorated with opulent rubies and gold and fanciful forms in vibrant colours. He hired freelance designers like Martinuzzi and Fulvio Bianconi regularly. Gio Ponti from 1927, Carlo Scarpa from 1932, Eugene Berman from 1951, Ken Scott from 1951, Franco Albini from 1954, and Massimo Vignelli from 1956 were the designers he commissioned.