How was this painted 600 years ago?

The Madonna of Chancellor Rolin depicts an elderly Chancellor Rolin kneeling before the Virgin Mary enthroned with the Christ child, set within an ornate Romanesque loggia framed by arches that open to a vast landscape beyond. Painted by Jan van Eyck in 1435, this masterwork captures an intimate religious scene with such luminous precision that it seems to transcend the canvas itself, utilizing meticulous layers of translucent glazes and unified light physics to prove that distant landscapes rendered at microscopic scale could maintain perfect optical coherence with the foreground, making the background cityscape feel as real and tangible as the figures in front. Beyond its depiction of spiritual devotion, the composition holds deep theological meaning, featuring carved biblical scenes of humanity's fall placed directly above Rolin's head and symbolic flowers throughout the garden, while a hidden self-portrait of Jan van Eyck himself peers from the distant fortifications...a signature that many art historians believe subtly declares the artist's eternal presence as witness to this moment of divine grace.