It takes a boot disk that will work on many systems, or at least the target systems. (the boot disk can be put on a cd or used on a floppy)
Then it's a matter of running scripts at boot that will do everything you did to get your LFS running, except it must account for any different hardware along the way. This is not an easy thing to do. And can't possibly be worth the effort. IMO
But hey, if your willing to do it then good luck. let us know when it's ready to test.
Building your own root boot disk with the tools you need to build an LFS system is a good place to start.
put your boot.img on the cdrom as an image so a floppy can be made from it for booting, and also make it the cdrom's boot image so the cdrom will also boot to it.
then if it's going to be automated you will need to have the scripts to install everything and also all the programs you want installed that are already built for the target systems.
The easy way
I think basically what we're talking about is an image of a working system that will work on most hardware. that you simply dd to the install partition.
so this what you need:
a boot image that supports most hardware
disk tools to allow the user to partition and dd
the image to copy over
however this is going to eliminate some things, like being able to choose what to install.
root boot disks
I like this one