Hi. I want make my own linux distro x64 with minimum components. I want to make it live USB with option to install on HDD + install mods in future.
It's simple...
Linux From Scratch. Except, well, it's not as simple as you might think. Forget about how to make a live USB until you've actually built a distro to work with. Start the race at the beginning, not at the end.
If you find actually building a distro is too hard, you might be able to fork an existing distro instead, so most of the hard work is already done for you.
This article was updated in 2017, but some of it may not be current anymore. Slax, at least, has changed how it is built... now based on Debian instead of Slackware.
Unfortunately, you won't find much detailed help here. Building from scratch, or even building a respin, is beyond the abilities of all but maybe a few of our users. If you want to be a developer, join some developer mailing lists and/or IRC channels and talk with those who are actively involved in projects like this. Most of us here are just not capable... we can only Google for you, and you should be able to Google for yourself.
Good luck!