An ice maker for a refrigerator appliance includes an ice making assembly defining a receiving chamber in fluid communication with an air duct and a mold assembly removably mounted to the ice making assembly. The mold assembly includes a frame configured for receipt within the receiving chamber of the ice making assembly, a heat exchanger mounted to the frame and defining a mold support surface, and a flexible mold positioned on the mold support surface that is supported by the heat exchanger such that the flexible mold is in thermal communication with the heat exchanger and defines a mold cavity configured to receive a liquid. The mold assembly is replaceable with alternate mold assemblies.