A Flexbox developer designs and develops responsive web layouts using the Flexbox model. They create dynamic user interfaces that change according to screen size, ensuring optimal viewing and interaction experience. They organize content with flexibility, controlling the alignment, direction, order, and size of boxes. They also solve complex layout problems with less code and greater compatibility across different browsers. They work closely with web designers and other developers to ensure the website's layout functions as intended. Their work is crucial in modern web development, as it enhances user experience through improved web page layout management.