Although several open-source, easy-to-assemble light-sheet microscope platforms already exist--such as mesoSPIM, OpenSPIM, and OpenSpin--they are primarily optimized for imaging large specimens and lack the resolution required to visualize sub-cellular organelles or cytoskeletal architectures. Conversely, commercial systems like Lattice Light-Sheet Microscopy offer improved resolution but are complex, expensive, and alignment-intensive. To address this gap, we developed Altair-LSFM, a high-resolution, open-source, sample-scanning light-sheet microscope specifically designed for sub-cellular imaging. By optimizing the optical pathway in silico, we created a custom baseplate with precisely positioned dowel pins to simplify alignment and assembly. The system integrates streamlined optoelectronics and optomechanics with seamless operation through our open-source software, navigate. Altair-LSFM achieves lateral and axial resolutions of approximately 235 nm and 350 nm, respectively, across a 266-micron field of view after deconvolution. We validate the systems capabilities by imaging sub-diffraction fluorescent nanospheres and visualizing fine structural details in mammalian cells, including microtubules, actin filaments, nuclei, and Golgi apparatus.