35mm slide holder / scanner

This is a contraption I designed to allow me to very quickly scan thousands of my parents 35mm slides. The slide drops in the small slot, put your phone in the back slot and have your phone display a white screen at full brightness (there are several free apps that can do this). Then use your dslr with an appropriate macro lens to copy the slide. I use a panasonic GH5 and a sigma 105mm macro lens. I set the camera to aperture priority mode at f8. I also enable the HDR mode in the menu to maximize the dynamic range. I white balanced manually on the lighted surface of the phone. Some film stocks looked better by manipulating the white balance a bit, but this provides a good starting point.
Personally, I mounted the contraption to a piece of wood and then mounted a manfrotto plate receiver at the other end. The manfrotto system allows about 3-4 inches of sliding front to back, so it's easier to get the slide to fill the frame at the given focus distance. The height can be adju