Previously, you would use a boot disc like iBoot to emulate the EFI layer, then boot the retail Snow Leopard disc and install. Since Lion is primarily suited for virtual distribution, the common approach is to buy and extract the Lion installer on an existing Snow Leopard system, then use xMove to set up a second partition with a bootable installer. From here, you would either use rBoot, or install the Chimera bootloader directly onto the USB stick.
Alternatively, you can use the regae Install DVD Maker to combine the Lion installer with the Chameleon bootloader and create an ISO that can be burned to DVD. It works well enough, but in my experience, the layout of the files on the disc is not at all optimal, so your optical drive will spend a ton of time seeking. It took upwards of an hour to install this way on a 3.3GHz i5 with 4GB of RAM.
Or, I guess you could just buy Apple hardware.
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