Guy, I did pretty much the same thing I angled the frame into 3 pieces, except I did not extend the front with the "Z" I was able to actually fit the front frame members (after some filing) into the hollow portion of rectangular styrene that I then glued to the adjoining frame.
everything looks great, are you just using straight salt or a mixture, I am using a mix of kosher table and baking soda. the fine grain in the baking soda helps give that textured look and adheres quite well.