Does it support UEFI systems??

No matter GPT or MBR...

Yes you can do LFS on both partition schemes. If you are on a system with GPT partition scheme, use gparted to create new partition else if you are on MBR use fdisk instead of gparted. And don't forget to enter the new partition on fstab so that you can mount that partition permanently.

What is and why is LFS

What is and why is LFS...

Linux from scratch aka LFS is the best tutorial or guide for making a custom linux os from source.

Using LFS we can make our own customized linux distro from source based only on our likes. Most of the famous linux distros like ubuntu, mint, etc. may contain programs or software's that are not needed by the user. And those unwanted programs use our system resources like harddisk space, memory, cpu time etc and make other programs starve for those valuable resources. Off course there is an alternative for such problems as you just thought rather than LFS like removing the pre-installed packages from the system. But always it is better to make your own os with a bundle of packages that you like .

Why is LFS?? answer is simple.. there is no one else out there for teaching us how a linux os is made or how a linux os can be made. Yes, LFS is a step by step guide which describes how a linux os can be made. If you need to know the working of linux you must made one and LFS make it simple. Here is the link for home page http://www.linuxfromscratch.org/lfs/