NEMO-GSL v1.0 is a three-dimensional hydrodynamic and ice configuration of Great Slave Lake (GSL), the deepest lake in North America and a central component of the Mackenzie River system, built on NEMO v5.0 with the SI<sup>3</sup> ice module. The configuration targets conditions absent from ocean and temperate large-lake setups: weak, temperature-controlled stratification, seasonal ice cover exceeding seven months annually, and water levels governed by riverine throughflow. Simulation domain construction required a basin-wide bathymetric product, generated by Universal Kriging of digitized nautical charts, sparse soundings and crowd-sourced depths onto a 1 km grid with 81 vertical levels. Adaptations from NEMO defaults include generic length scale k–ω closure with the Canuto B stability function for weakly stratified freshwater, adjusted SI<sup>3</sup> snow conductivity and ice albedo for freshwater ice under prolonged cover, and a modified river routine in which outflow is computed from mean lake level using monthly stage–discharge relationships, with a hydrostatic correction for the ice and snow load applied in winter. The configuration is forced by CaSR v3.2 atmospheric reanalysis and MESH-derived runoff. Evaluation over 1998–2001 against thermistor profiles at six stations, eddy-covariance evaporation, satellite-derived lake surface water temperature (LSWT) and ice phenology yields water-column RMSE of 2.08 °C, LSWT RMSE of 1.68 °C, mixed-layer depth (MLD) MAE of 6.42 <em>m</em>, seasonal evaporation totals within 0.25 % of observations, and ice freeze-up and break-up errors of 1 and 2 days, respectively. Forcing sensitivity experiments reveal wind forcing as the dominant control on simulated mixed layer depth. The bathymetric reconstruction methodology, ice–turbulence parameterization protocol, and river-forcing coupling strategy developed here are independent of GSL-specific inputs and are intended for reuse in other data-scarce, ice-covered lakes. Together, these developments are designed to establish a replicable workflow for subarctic lake modeling, extending NEMO’s application domain beyond the contexts of ocean and temperate large lakes.