While I'm waiting for a print to complete I usually load up a few models on SD Cards and stick them near the printer, when the print finishes I pull the old card and put the new in. Sometimes I forget to take the old one away and end up with it in the pile of 'next' cards. I don't mark my SD cards or name the files on them so I end up clearing the cards and starting again or just guessing.

I designed this to hold 5 SD cards on my IKEA lack enclosure. This means I can queue my spontaneous prints and have some form of order.

I mark the enclosure door with the SD card contents (Lack marker holder here https://www.prusaprinters.org/prints/32754-lack-table-dry-wipe-marker-holder)

When a print is complete I wipe it off (Lack eraser here https://www.prusaprinters.org/prints/32753-lacktable-whiteboard-eraser-holster)

Print instructions

I was afraid that this would sag and the cards would not fit, so I printed it in the orientation it would be used. This worked out well and I had no issues with my prints.

I don't think the infill is important here, I used 15%
I printed in PETG with a 0.2mm layer height
I used a Prusa i3 Mk3s with the textured steel sheet
No Skirt or brim necessary
No supports necessary