A plurality of camming surfaces (116) are actuated to move against the top portion of the side walls (38) of a container (36) to turn such top portion in an outward direction relative to the interior of the container sufficiently to enable the seal profile (90) of the top tool assembly (30) of a sealing apparatus (22) to press the outwardly disposed side wall top portions downwardly against an abutment formed by a bottom tool assembly (32) so as to create a horizontal, outwardly disposed sealing flange (40) to which a top film (34) is applied for closure of the container.