The most normal method for this is to do this through PXE; whether the machines come out of the box set up for PXE and with populated hard disks or not is dependent entirely on how you purchase them, so it may be necessary to alter BIOS configurations first, but most genuinely blank machines can PXE-boot directly to the management client without needing first to have an operating system or any installed software.
Ghost has been used to manufacture machines on assembly lines for well over a decade, and that process (whether using Ghost or one of its various imitators) is generally how they get from a genuinely blank factory state to the in-the-box state with an installed operating system. Once they have content on the hard disk, newly-manufactured machines are generally BIOS-configured to prefer to boot from hard disk, but it's a trivial tweak to adjust the PXE boot priority as part of unboxing them.