Making DOS USB images on a Mac

I needed to run a BIOS flash utility that was only available for DOS. To complicate matters, the server I needed to run it on doesn't have a floppy or CD-ROM drive. I figured I'd hop on the Internet and download a bootable USB flash drive image. Right? Wrong.I found a lot of instructions for how to make such an image if you already have a running Windows or Linux desktop, but they weren't very helpful for me and my Mac. After some trial and error, I managed to create my own homemade bootable USB flash drive image. It's available...