Step 1In a blender, finely grind the coriander seeds with the oil (alternatively, grind the coriander seeds in a coffee grinder or spice mill, then combine with the oil).
Step 2Transfer the oil and ground seeds to a clean bowl or jar, pressing plastic wrap onto the surface of the oil to reduce contact with the air (alternatively, transfer the mixture to a sealable plastic bag, pressing out the air before sealing).
Step 3Set the mixture aside in a cool, dark place, to give the spice time to infuse the oil, about 2 days.
Step 4Strain the oil using a cloth-lined strainer to catch all the spice particles. Refrigerate, covered, up to 1 week, or freeze up to 6 months.