The carvings are English in a gothic style (where there was no Renaissance). They are carved in alabaster which was quarried in Nottinghamshire. What is interesting is that when painting in the same century, the Flemish artist Rogier Van Der Weyden painted his figures as though they were occupying a foot-wide space projecting out to plane of the painting. Employing, very clearly, a far greater degree of naturalism than the English sculptors did, he nevertheless painted a backdrop so as to eliminate the chance of the illusion of too great a depth.
All of this helps to ensure that there is a balance between adherence to natural appearances, which communicates visual realities; and stylization through some departure from strict naturalism, which lends a symbolic quality to the image and communicates invisible realities. Keeping the image to a space that doesn't deviate far from the plane of the painting and restricting the illusion of depth communicates the presence of the heavenly dimension, which is outside space (and time).
