Spectral energy distribution of GRB 210312B and the residuals from the temporal and spectral fit model presented in Fig. 9. The points show the data after the temporal evolution is removed, revealing the intrinsic spectral shape. The griz photometric measurements of both host galaxy components are shown (points), along with a representative galaxy template spectrum (solid line) for comparison. The dashed line shows our simplified model of the host system used for host contribution corrections during afterglow fitting.