As far as the foundationless frames go, I am buying the side bars and building the rest. Bottom bars should be really easy to do, since they are just rectangles of the appropriate dimensions. The top bars will be slightly more challenging, but I will not have to deal with the groove as in your photos. I'll rip larger stock down to the proper dimension, then vice-grip a bunch of top bars together and make the notches to accept the side bars. I will then turn the top bars 90 degrees and reapply the vice grip. Now the cutouts for the frame rest. The last part of the process will be to cut the corners off of the longside on the underside of the top bar to make the central ridge. Since I am making about 5-600 of these, it should be worth messing around with changing all of the re-adjusting of the table saw, adding the dado blade, taking it off, etc.