For the application of biopolymers, the high processing temperature, high viscosity, and easy thermal decomposition during processing have been challenges to researchers. Our research has shown that 1-ethyl-3-methylimidazolium acetate ([C2mim][OAc]) has a significant plasticisation or dissolution effect on starch, and can reduce the crystallinity and make the amorphous phase more mobile. Based on this, we developed a facile and energy-saving process to create starch-based electrically conductive films. A one-step compression moulding process was used with a mild temperature (55 °C or 65 °C) to prepare films with different IL contents (0.18 or 0.21 IL : 1 starch hydroxyl, mol/mol), which were then conditioned under either 33% or 75% RH. We demonstrate that the structure and properties of the processed starch-based material can be well tailored by the IL content, processing temperature, and/or post-processing RH. In particular, the XRD results suggested a higher temperature could allow stronger interactions between starch and [C2mim][OAc], facilitating the rearrangements of starch molecules to form new crystals. However, with both high [C2mim][OAc] content and RH, the interactions of these liquids with starch hydroxyls could dominate, inhibiting the interactions between starch molecules. On the other hand, all the samples had good electrical conductivity (>10−3 S/cm). For the samples with the same starch content and conditioned at the same RH, a lower processing temperature led to a higher electrical conductivity. A higher processing temperature allowed [C2mim][OAc] and water molecules to strongly interact with the starch, which might have reduced the extent of ion pair dissociation. Furthermore, a general trend could be identified that either an increase in RH or [C2mim][OAc] content could increase the electrical conductivity, with the effect of RH being more significant. These findings could be useful for the development of advanced biopolymer-based materials.