OK to unmount the SD card.
Eject the SD card from your Nintendo Switch, plug it into your computer.
Navigate to the
backup\XXXXXXXX folder, and copy out of there any of the
BOOT1 files somewhere on your computer, keep them all in the same folder.
Eject your SD card from your computer, plug it back into your switch. Repeat 1 through 4 until you have a full backup. Should be roughly 29.2GB.
If you get this popup at the end you completed the steps properly.
A full proper backup consists of 15-30
rawnand.bin files either 1GB or 2GB each, and a
BOOT1 file. The backup should be 29.2GB~ in size.