Intel has stated in Intel Support Document #000024603 that they don't enable firmware support for booting from SD cards on any of the NUC line of devices.
There is an exception though, provided that you are willing to switch off UEFI bootloader support and rely on the Compatibility Support Module (CSM) for "Legacy Boot" mode emulation. Having adjusted those settings (by pressing the F2 key at startup to enter the BIOS Setup menu) you can then boot from the SD card slot, provided you format the card to identify itself as bootable like a flash drive would.
To be doubly-certain that the device is, in fact, bootable under Legacy Boot mode, you can use the
DISKPART utility to format it and the
bootsect command to verify the MBR flags before writing the install image to it (as outlined by Microsoft).
- From an elevated Command Prompt window (right-click on the Start button and select "Command Prompt (Admin)"), enter the following sequence of directives (replacing any instance of the letter X with the numeric entry that corresponds to your SD card in the list shown by the preceding command):
DISKPART> list disk
DISKPART> select disk X
DISKPART> convert mbr noerr
DISKPART> create partition primary
DISKPART> select partition 1
DISKPART> format fs=ntfs quick
DISKPART> assign noerr
DISKPART> list partition
list partition step just before
exit, you should see the new partition with a * in the Active column as well as its drive letter in the column listing those assignments. Armed with that drive letter, you can then set the bootable flag in the Master Boot Record (MBR) manually, exactly as would be found on a USB flash drive by whatever utility was used to write the image to it.
- Again from an elevated Command Prompt, issue the command:
C:\> bootsect /nt60 E:
replacing the letter E with the drive letter assigned to your SD card (which can be confirmed from the File Explorer or the Disk Management app located in the Administrative Tools folder of the Control Panel, if not using the same Command Prompt window).
Now it's only a matter of mounting the install image (right-click the image file and select Mount from the File Explorer) and copying the contents to the SD card.