A method for making a pocket filter assembly is provided. Two side and two end header elements each having a pair of longitudinally extending side walls and a longitudinally extending bottom wall forming a longitudinally extending channel are joined at ends forming a rectangular header with two opposing sides and two opposing ends. The bottom wall and side walls of each of the opposing sides and the bottom walls and said side walls of each of said opposing ends become adjacent forming a rectangular header with a continuous bottom wall and continuous inner and outer side wall having a continuous channel therein. An upstream perimeter portion of a pocket filter element is inserted in the continuous channel and a liquid polymeric material is placed therein. The polymeric material is solidified forming a header frame having the upstream perimeter portion of the filter element unitary therewith.