We will install a Debian ISO on a usb or hard drive. And then convert the bios to UEFI
(This example can also be entirely done in a with Virtualization)

Tools you may need:

• A USB or cd for putting the OS on it
• and other USB or hard drive as your main installation drive.
• uefi compatible motherboard

After writing the iso on a usb and booting from it and install it on a hard drive with the graphical interface.
Because you can’t (easily) build uefi if you are not booted from it, we will download and iso from a linux distro that provides iso with uefi already on it(evolve os, manjaro, semplice 6, Slackel,…) and rewrite on the first usb. Boot from it.
With gparted GUI resize your main boot partition from 243 to 200.
create a fat32 primary partition for 43mb. Give it the boot and esp flag

gdisk /dev/sdb
r
f
w

and now gdisk -l /dev/sda

should give you:
MBR: protective
BSD: not present
APM: not present
GPT: present

Mount your hard drive on /mnt (sda is bootable usb and sdb is your hard drive and it may differ in your case)
mount -t ext4 /dev/sdc5 /mnt

or if it is encrypted:

cryptsetup luksOpen /dev/sdb5 sdb5_crypt
mount -t ext4 /dev/mapper/example-root /mnt
mount /dev/sda1 /mnt/boot
mount /dev/sda2 /mnt/boot/efi
for i in /dev/ /dev/pts /proc /sys ; do mount -B $i /mnt/$i ; done

get a chroot environment:

chroot /mnt
type blkid to get the UUID of your fat32 partition
edit /etc/fstab and add the following line with your UUID

UUID=94D0-2462 /boot/efi vfat defaults 0 2

For internet access inside chroot:
cp /etc/resolv.conf /mnt/etc/resolv.conf