In Resin Transfer Molding (RTM), resin precursors of thermoset or, more recently, thermoplastic polymers are generally employed, raising issues related to the chemical reaction taking place during and after part processing. In this study, already polymerized polyamide-6 with low melt-viscosity (~30 Pa·s at 280 °C), is injected at low pressure (<30 bar) in a custom-made mold, so as to impregnate glass fabric preforms via in-plane impregnation. Composite plates were produced using interply spacers acting as flow-enhancers. A three-step impregnation strategy, involving fast in-plane resin injection, a successive saturation step through transverse flow, followed by further micro-saturation caused by the collapse of the spacers, ensured industrially relevant impregnation kinetics. The influence of the spacer, the saturation time, pressure and temperature on the process kinetics and part quality were evaluated with three-point bending tests as well as microstructural analyses. Optimum processing parameters were identified and scaled up for a given part geometry.