A method of molding a flange uses a first tool element and a second opposing tool element. The first tool element defines a negative of at least a portion of a first side of a flange, and the second tool element defines a negative of at least a portion of the second side of the flange. The method includes providing a set of blocks for insertion into a plurality of recesses in the second tool element, the set of blocks insertable in a plurality of configurations, each configuration defining a negative of a set of retention features on the second side of the flange. The plurality of configurations define differing configurations of retention features on the second side. The method also includes inserting at least some blocks into the second tool element to form a selected one of the plurality of configurations, and performing injection molding using the first tool element and the second tool element.