How to sign fonts?

[Siddh Raman Pant]

I recently made a separate partition for /boot because I migrated
my root to btrfs, and this has caused my grub theme to not show
the correct font now.

So I tried to load the font using loadfont on command line, which
throws up "prohibited by secure boot policy". But secure boot was
enabled earlier too, so I'm not sure why this happened.

Some discussion mentioned grub can load signed .pf2 fonts. So, how
to sign the fonts in the first place?

Also, if someone could tell why the font stopped working on making
a separate /boot partition, it would be very helpful.

Thanks,
Siddh