If you printed my Noel Holiday Christmas Train, then surely you must need a way to store it once Christmas is over. This was designed in keeping with the original slide in cover/tray combination.
Print the tray with low infill, 1.2mm walls and 1mm top layers. I went with [Ironing] [Only on the Top Layer], but that is optional. Then print *sleeve.png* at 300dpi, 100% on 8-1/2"x14" card stock (for a muted, matte finish) or photo paper (for a bright, gloss finish). Fold on the obvious transitions and glue the solid color tab to the back of the side panel, making a sleeve. Once the glue is dry, the tray will slide in and out with relative ease, giving your Holiday Train a safe home for the not-holidays.