I rally don't know why people call these 'disros'. They're not. They're liveCDs populated with software you want to run, or PXE or USB, etc.
The same thing is available at instalinux.com - spin your own liveCD? NO! They call them distros, and their not. The distros are Ubuntu or Deb or Fedora, etc.,
Even LFS isn't REALLY building your own distro - it's building your own UNIX system with the Linux kernel.
In order to build your own distro, what you need to take into consideration is this:
1.) it must have a method for distribution. i.e., an installable CD (or bootable media that connects to an NFS or FTP server, etc.) with an installer that when 'distributed' to people in the marketplace, allows those users who bought or downloaded your distro to boot their machine, partition their hard drives, select software, and then actually install the operating system onto their hard drive - like a Windows install CD or a Slackware install CD/DVD.
2.) You should have a package management utility, so that the people who procure your distro can at anytime install, upgrade, or uninstall software packages.
3.) You should maintain the distro - meaning that as new kernels come out and new versions of software, the next version of your distro will have those components as part of the installation of the OS.
LFS is a good start for building yourself a distro from scratch, or you can begin with and existing distro, say, one that ...