I got my Larkbox booting from a SSD this morning.
It worked for me, it might not work for you:
I cloned the Windows partition and recovery partition from EMMC to SSD.
Went into the bios to set that I could boot from the USB. And disabled the EMMC.
Ran windows installation from USB <= I had to put an extra fan on it because the fan wasn’t running during Windows installer, it crashed the first time.
Windows took care of getting it to boot from the SSD.
I tried to get it to do a windows repair, but it refused to do it. Had to do a clean install. It said it would put the old files in “windows.old”.
I timed the boot before and after and it booted in 20 seconds from the EMMC, it takes 24 seconds from the SSD. SSD benchmarks pretty well.