In gray, in the photo: A longer version of jonnig’s original. I used Tinkercad, imported the STL, repeatedly unioned with rectangular holes to break up the original into pieces, then stuck the pieces back together.
Slic3r said that it fixed the resulting .stl when I sliced it.
Since Tinkercad is web based, the source code is also on the web:
https://www.tinkercad.com/things/gYfrWA22fcY-v2standxlclearance
Print Settings
Printer Brand:
Prusa
Printer:
i3 MK3
Supports:
No
Resolution:
0.15mm. Standard 0.4mm nozzle
Infill:
20%
Filament: Prusa PLA Gray
Credits:
DavidPhillipOster