We present the opto-mechanical design of SAMOS, the SOAR Adaptive-Module Optical Spectrograph. SAMOS is a multi-object, reconfigurable-slit spectrograph designed to fully exploit the Ground Layer Adaptive Optics (GLAO) laser guide system of SOAR, i.e. the SOAR Adaptive Module (SAM). While it is designed to maximize sensitivity, it can also efficiently operate in regular seeing limited conditions. It will operate in the optical spectrum, covering a bandpass of 400 - 950 nm, in two exposures, utilizing four grims: two to produce low resolution spectra, i.e. R » 3000, as well as two narrow bandpass, high resolution spectra at R » 10, 000. The instrument uses a large-format Digital Micromirror Device (DMD), a programmable array of miniature mirrors, as a programmable slit to steer light from the telescope focal plane into either a spectroscopic arm or an imaging arm. The DMD can be reconfigured in seconds, allowing a vast range of slit widths and lengths; each being a multiple of mirrors wide and long. In SAMOS this facilitates the collection of up to as many as 200 spectra simultaneously, allowing a multitude of slit configurations, which can be optimized for seeing and science, and, at the same time, enables parallel science imaging of non-dispersed targets through a suite of broad and narrowband filters. SAMOS is a very compact instrument, by necessity. It attaches to the SOAR Adaptive Optics Module (SAM), fitting in a location with limited space, requiring a highly folded, compact optical design. This paper discusses the opto-mechanical design of SAMOS, including the overall system design as well as detailed descriptions of the optical mounts and mechanisms.