Epoxy composites reinforced with natural fibers are a research area that has been growing tremendously in recent years, with increasing reports providing a better understanding of the interactions within such structures, resulting in newer and more specialized applications. This article presents a comprehensive study on the design and application of ionic liquids (ILs) in the development of flax fiber-reinforced epoxy composites with tailored mechanical properties. Three distinct ILs, namely 1-hexyl-3-methylimidazolium dicyanamide [HMIM][DCA], 1-hexyl-1,4-diazabicyclo[2.2.2]octan-1-ium dicyanamide [DABCO-C6][DCA], and trimethyloctadecylammonium dicyanamide [N11118][DCA], were strategically engineered to incorporate longer carbon chains, with the primary objective of influencing the mechanical parameters of the resulting composites, specifically aiming for enhanced flexibility and resistance to bending and stretching. Using these designed ILs, two mixtures were developed and crafted to facilitate the effective curing of epoxy resin, which was examined using Differential Scanning Calorimetry (DSC). Investigation of the resin crosslinking process revealed that the mixtures of ILs exhibited a lower total enthalpy of thermal conversion than single-IL systems. Moreover, shifts in the polymerization onset temperatures were observed for the mixtures, with some systems displaying dual temperature peaks during crosslinking, indicative of potential parallel polymerization reactions.