The High Angular Resolution Monolithic Optical and Near-infrared Integral field spectrograph (HARMONI) is planned as a first light instrument for the Extremely Large Telescope (ELT). The Instrument Control Electronics (ICE) subsystem plays a vital role in HARMONI, housing all control devices and ensuring they function optimally. However, limited space within the instrument necessitates a unique design approach for the electronic cabinets. This paper details the design of these bespoke cabinets, emphasizing the thermal analysis and insulation technologies implemented to maintain proper operating temperatures for the electronics within the compact instrument volume.