A cooling system assembly method including: providing a support fixture having a multi-level support surface and multiple positioning dowels extending therefrom; positioning multiple liquid-cooled cold plates on the support surface employing the multiple dowels, the dowels providing relative positioning and alignment of the cold plates for facilitating subsequent coupling thereof to electronic components to be cooled; sealing multiple coolant-carrying tubes in fluid communication with the cold plates; and sealing a header subassembly to the coolant-carrying tubes to provide an assembled liquid-based cooling system. In operation, the support fixture facilitates shipping of the assembled cooling system by maintaining the components in fixed relation. A transfer fixture is employed in removing the cooling system from the support fixture and placing the cooling system in engagement with the electronics system. The transfer fixture includes multiple clips engaging and holding components of cooling system in fixed relation when removed from the support fixture.