His artistic method relied on a system he called Pure Design. Ross rejected the idea that art was purely intuitive. He developed mathematical formulas to determine the placement of lines and the harmony of tones. He created specific colour scales to remove guesswork from the process. This systematic approach resulted in works with a quiet, disciplined order. His paintings feature muted palettes and weighted compositions that prioritise formal structure over narrative drama.

Modern collectors value the work of Ross for its clean geometry and intellectual rigour. His studies of colour and form anticipated the minimalist movements of the later twentieth century. Because he focused on the principles of arrangement, his prints suit contemporary spaces. The neutral tones and balanced proportions of his watercolours provide a sense of calm. His work links early craftsmanship with the structured aesthetics of modern design.