Finally got this set of commands to generate a bootable hybrid image, but would like to write it directly to the drive instead of a file, if possible:
xorrisofs -o /tmp/output.iso -iso-level 3 -full-iso9660-filenames -volid "TESTVOL1" \
-c boot/isolinux/boot.cat \
-b boot/isolinux/isolinux.bin \
-no-emul-boot -boot-load-size 4 -boot-info-table \
-isohybrid-mbr /usr/lib/ISOLINUX/isohdpfx.bin \
-partition_offset 16 "/tmp/test/boot" \
-eltorito-alt-boot -e EFI/BOOT/efiboot.img -isohybrid-gpt-basdat \
-graft-points /data="" code=/tmp/code