The increasing demand for high-performance electric motors, driven by the rapid adoption of electric vehicles, necessitates effective thermal management techniques. Efficient dissipation of heat generated in the copper windings is critical for the safety, efficiency, and reliability of electric motors. Heat must be transferred from the current-carrying copper windings to the metallic stator body through an electrically insulating material called the slot liner. But little research has focused on the interactions between the slot liner and the windings in the stator-slot liner-winding assembly in terms of dissipating heat from the windings. This study examines the impact of compression of the slot liner on the thermal resistance across the stator-winding assembly considering two common slot liner materials: Nomex® 410 and Kapton® MT+. To do so, we developed a mock stator-winding assembly by stacking a rigid, grooved copper piece that mimics the windings, the slot liner, and a rigid silicon piece that imitates the stator, along with a reference material used to quantify heat flow through the assembly. Steady-state temperature gradients are established across the stack, and the resulting two-dimensional temperature maps are captured using infrared (IR) microscopy and analyzed to calculate the total thermal resistance across the assembly. Tests are repeated at several levels of compression and with increasing compression, the area-normalized thermal resistance of the winding-stator interface with a Nomex®410 slot liner decreases by 14.9% (from 94 to 80 cm²K/W) and with Kapton® MT+ decreases by 68.0% (from 50 to 16 cm²K/W). Ultimately, this research provides insight into the effects of slot liner material and compression level on the thermal management of electric motors and provides guidance on optimum system configuration. Reducing the total thermal resistance of the stator-winding assembly can reduce temperatures within the windings, which, in turn, improves the longevity and efficiency of the motor.