The materials sintered with FS are determined by considering temperature, time, energy, cost, environmental pollution, and human health. In this study, cast iron slag wastes (CISW) were utilized in powder form and sintered using flash sintering (FS). The outcomes of both FS and conventional sintering (CS) processes were assessed regarding their physical, chemical, and mechanical properties. The CS process was performed at 1000ºC for 4 h. FS experiments were conducted under 20, 25, and 30 V/mm electric fields. CISW was sintered using the FS method resulting in lower temperatures and shorter processing times, thus yielding energy savings. Through this method, it was observed that the interatomic spaces narrowed due to the electric field and temperature applied to the sample. Physical, chemical, and mechanical tests (3-point bending and hardness) were carried out on all sintered materials. Experimental results indicated that the sample sintered under the 20 V/mm electric field at 517ºC for 15 s exhibited better mechanical properties compared to CS. On the other hand, the sample flash sintered under 30 V/mm electric field had lower temperatures (478ºC) compared to all FS processes that were carried out with perfect intergranular interactions. However, the mechanical properties were lower than the others because the structures may have passed into the liquid phase. Consequently, it has been proven that this product obtained from CISWs can be used in floor and wall tiles according to ISO10545-4 and BS—EN14411:2016 standards. It has better mechanical strengths than all other sintering processes with FS under 20 V/mm electric field.