A method of forming a frame around a membrane stack for a laterally-fed membrane chromatography device is provided. The method includes placing a membrane stack having one or more membrane layers on a bottom surface of body of a master mold, the body having opposed side walls and opposed end walls, the opposed side walls spaced apart by a distance greater than a length of the membrane stack, the opposed end walls spaced apart by a distance greater than a width of the membrane stack; placing a cap on the body of the master mold to enclose the membrane stack in the master mold, the cap having at least one opening for injecting a material into a space defined by the end walls of the master mold, the side walls of the master mold, end walls of the membrane stack side walls of the membrane stack, the bottom surface of the body and an inner surface of the cap; injecting the material into the space around the membrane stack; and curing the material to form a frame around the membrane stack.