Panels a–d show the four steps to isolate the fingerprint range of COM ices between 6.8 and 8.8 μm from the original JWST/MIRI-MRS spectrum of B1-c: (a) fit a global continuum and convert the spectrum to optical depth scale; (b) subtract silicate features at ~9.8 and 18 μm; (c) trace a local continuum in the 6.8–8.8 μm range to isolate the weak bands of COM ices from other strong features; and (d) trace a baseline of the gas-phase lines in absorption to restore the band profiles of ices. Panel e shows the isolation of the CH₃OH ice band at 9.74 μm by tracing a local continuum. The orange-shaded regions in panels a and e show the selected wavelength ranges for the polynomial fitting.