What would be the equivalent of this in UEFI? I mean is there a one page tutorial on booting with UEFI by writing a few lines of assembly?
You may find it interesting.
Basically you won't bother writing a bootloader with UEFI, since it already provides that feature. Instead you'll get right at working on your OS.
which is certainly not an easy tutorial to follow. Seems like more robustness tends towards a greater barrier to entry.
It's a lot easier and nicer to use either UEFI or a Multiboot-protocol bootloader (GRUB, or qemu/bochs built-in bootloader). That also means you will be starting in long mode or protected mode.
In order to work with bare metal efficiently, you need to get a debuggable and bootable ELF image up and running as soon as possible. Once you can attach a remote GDB debugger to Qemu, you get things done much faster than using the Qemu/Bochs monitor/debugger.
Anything more complex than a hello world example is easier with UEFI or multiboot than BIOS boot sectors. You will need a linker script and a build script but things will be much easier after the first steps.
I made this pull request for someone else's bare metal project to add debuggable ELF images. It's a small but practical example: