Terminal: create bootable USB from iso

How can I create a bootable USB stick from an iso image?

I thought dd should do the work, but so far I were unsuccesful.

This is what I've tried:
umount /dev/sdx
deleted every partition on sdx with Gparted
dd if=/path/to/iso/some_file.iso of=/dev/sdx bs=1024K


The file is a bootable BIOS update utility, but since my laptop does not have a CD/DVD drive I want to deploy this image on a USB stick.
However, when I have a look at sdx in Gparted, it tells me that it's size is 0 and no partitions have been created, although dd claims it has written 26MB to /dev/sdx.

I also tried to create a FAT32 partition (full size) with Gparted and then let dd copy onto this partition: dd if=/path/to/iso/some_file.iso of=/dev/sdx1. Did not work either.

The USB Stick is ok, I can write and exchange data between my laptop and computer with it. (Actually it is the same USB stick that I used to install Manjaro on my laptop before)

What am I doing wrong?