He was immediately appointed at Yves Saint Laurent as Hedi Slimane's first assistant for the Rive Gauche Homme line.

[9] In April 2018, Van Assche was confirmed as the new creative director at luxury brand Berluti, another LVMH company, following the departure of Haider Ackermann.

In 2021, Van Assche became a mentor of the Master in Creative Direction at Polimoda fashion school in Florence, Italy.

[15] In 2022, Van Assche created a collection for Chinese kidswear company Balabala, with products for girls and boys ages three to 14.

[16] Van Assche's style icons are Jean Cocteau, for his classic coats and eccentric manner; Pina Bausch, who wore boots for dancing; and Sean Penn and Johnny Depp.