Methods for forming a stock roll including a folded film within another folded film include combining the films and winding them into the stock roll. In particular, one or more implementations of a method of forming a stock roll involve combining films on an extrusion tower. Thus, implementations of the present invention can greatly reduce costs and space requirements, while allowing a single stock roll to feed a bag-making machine in order to produce bag-in-bag structures. One or more implementations further include stock rolls including a first folded film within another folded film.