Restoring your Switch to stock WITHOUT a NAND backup.
Just use Haku33, it is this but automated and safe. There is no reason for you to manually follow this process, it is dangerous!
Procedure by Nevercholt Tech (https://www.youtube.com/watch?v=gVjF_MKjSv8) - transcribed by Karunamon
Note: This procedure is somewhat advanced and, if you screw up, you are likely to hard brick your switch. *Proceed with caution!
Also note that this is a full reset. All save data, installed apps, everything will be lost.