Printing: Should be obvious how to orient these, but I printed the slider flat, and the case open-side-up. 100% fill because there was basically no difference in time due to the thinness, and they're such fragile parts anyways. Post-Printing Run the top of the tray over sandpaper a few times to smooth it off checking fit as you go until snug. Shouldn't have any problem with it falling out if you do it properly.