  We present the development of a Skipper Charge-Coupled Device (CCD) focal
plane prototype for the SOAR Telescope Integral Field Spectrograph (SIFS). This
mosaic focal plane consists of four 6k $\times$ 1k, 15 $\mu$m pixel Skipper
CCDs mounted inside a vacuum dewar. We describe the process of packaging the
CCDs so that they can be easily tested, transported, and installed in a mosaic
focal plane. We characterize the performance of $\sim 650 \mu$m thick,
fully-depleted engineering-grade Skipper CCDs in preparation for performing
similar characterization tests on science-grade Skipper CCDs which will be
thinned to 250$\mu$m and backside processed with an antireflective coating. We
achieve a single-sample readout noise of $4.5 e^{-} rms/pix$ for the best
performing amplifiers and sub-electron resolution (photon counting
capabilities) with readout noise $\sigma \sim 0.16 e^{-} rms/pix$ from 800
measurements of the charge in each pixel. We describe the design and
construction of the Skipper CCD focal plane and provide details about the
synchronized readout electronics system that will be implemented to
simultaneously read 16 amplifiers from the four Skipper CCDs (4-amplifiers per
detector). Finally, we outline future plans for laboratory testing,
installation, commissioning, and science verification of our Skipper CCD focal
plane.
