Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:5845587.
This is a box insert for the game Psychic Pizza Deliverers go to the Ghost Town. It's a one-piece insert because you have to remove everything from the box to play the game. (The box is part of the game.) Also, the insert does not completely fill the box in length or width, but it has a lip on two sides which hold the insert firmly in place when the player boards are added on top. The player boards also keep the slotted pieces in place while the lid is on, so this insert will hold everything in place when stored vertically or even upside down.
The insert is 250mm wide, so you'll need a printer with a fairly large bed, or you'll have to cut it smaller as you see fit. This just barely fits on my Bambu X1C. Also, the tolerances are fairly tight on the slots and the top-most edges, so if your printer isn't very dimensionally accurate you might need to adjust the corresponding values in the .scad file and generate a new .stl file.
Finally, this is not a particularly filament-efficient design at around 300g of PLA+.
This is my very first published Thing, so please forgive any faux pas. I've included the OpenSCAD file I used to create this. Feel free to use this for any non-commercial use.