I don't use Slayer's (with the exception of formatting a new hard drive) so I really don't know about Slayer's flashing the Cromwell BIOS.. If it does, more power to it, if it doesn't, then, that's because it's basically crap (other than the fact that it formats and partitions hard drives)...
Anyways, for the best interest of yourself in mind, it would be far greater for your learning pleasure (and I really do mean this) if you read the tutorial on creating a BIOS CD. It's really more fun if you do the work yourself and not rely on a auto-installer. Also, you'll learn something new and how things work. In the end, you'll get more out of it if you do it yourself.
If you want Slayer's to do it, then that's your decision, but about 98% of the members here will tell you to learn how to do it, then try.