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The Molecules with ALMA at Planet-forming Scales large program (MAPS LP)surveyed the chemical structures of five protoplanetary disks across more than40 different spectral lines at high angular resolution (0.15" and 0.30" beamsfor Bands 6 and 3, respectively) and sensitivity (spanning 0.3 - 1.3 mJy/beamand 0.4 - 1.9 mJy/beam for Bands 6 and 3, respectively). In this article, wedescribe our multi-stage workflow -- built around the CASA tclean imagedeconvolution procedure -- that we used to generate the core data product ofthe MAPS LP: the position-position-velocity image cubes for each spectral line.Owing to the expansive nature of the survey, we encountered a range of imagingchallenges; some are familiar to the sub-mm protoplanetary disk community, likethe benefits of using an accurate CLEAN mask, and others less well-known, likethe incorrect default flux scaling of the CLEAN residual map first described inJorsater & van Moorsel 1995 (the "JvM effect"). We distill lessons learned intorecommended workflows for synthesizing image cubes of molecular emission. Inparticular, we describe how to produce image cubes with accurate fluxes via the"JvM correction," a procedure that is generally applicable to any imagesynthesized via CLEAN deconvolution but is especially critical for low S/Nemission. We further explain how we used visibility tapering to promote acommon, fiducial beam size and contextualize the interpretation of signal tonoise ratio when detecting molecular emission from protoplanetary disks. Thispaper is part of the MAPS special issue of the Astrophysical JournalSupplement.

Molecules with ALMA at Planet-forming Scales (MAPS) II: CLEAN Strategies for Synthesizing Images of Molecular Line Emission in Protoplanetary Disks