In 1924 he moved to Paris to study under Fernand Léger and Amédée Ozenfant at their newly founded Académie Moderne, where he developed a style of painting at first resembling Léger's, though soon became greatly influenced by Ozenfant's Purist style. In 1925 he met Le Corbusier and was commissioned to create murals for a cinema he was working on, though the project was eventually shelved, and in the same year he was recommended by Ozenfant to create murals for the planned library annex to Erich Mendelsohn's Einstein Tower. Although Mendelsohn eventually abandoned this later project, an example of the designs from the series of paintings that Carlsund had prepared for the Einstein Library - the suite "Rapidité" - was realized in a mural at the Stockholm restaurant Parkrestaurangen Lilla Paris, in connection with the Stockholm Exhibition in 1930. In 1926 he was invited by Katherine Dreier and Société Anonyme to participate in her exhibition "International Exhibition of Modern Art" at the Brooklyn Museum in New York City., featuring both his mural projects, and over the following years he exhibits several times in Paris, also again in New York at Jane Heap's Little Review Gallery (1928), the Arts Council (1928), and the Rand School (1931). As he met Piet Mondrian, Theo van Doesburg and the circle of radical artists working in the Neo-Plasticist aesthetic, he came to adopt an increasingly reduced vocabulary of abstract rectilinear form, as well as being more and more affected by Constructivism.