Put pork fat in a medium pot. Add 1/3 cup water. Heat over very low heat, stirring occasionally, or until chunks of fat have liquefied and reduced in size by at least half (4 hours). Remove from heat and strain through a cheesecloth-lined fine-mesh strainer into a heatproof container. Let cool completely.
Make ahead: Up to 2 months, chilled; frozen, up to 1 year.