Downgrading from 11.1 to 10.3

I'd like to downgrade from 11.1 back to 10.3. I feel 10.3 booted faster and had better support for Xorg based desktops

I used freebsd-ugrade if that helps
I would suggest finding the root cause of your issues instead of downgrading.
I don't see any reason why FreeBSD 11 should work significantly worse than FreeBSD 10 if it's configured properly.
If you report your hardware and provide your configuration files (/boot/loader.conf, /etc/rc.conf, xorg.conf), most likely, people here will help you rectifying it.
And, if after that you still decide to downgrade, the procedure is the same as for any other system: restore your backup from before you upgraded. If you don't have a backup, reinstall.
Can you please share the steps
Others already did: either you backup all your stuff and re-install or you use the rollback feature. I suppose you could even "wing" it and simply slap the 10.3 source code on there after which you simply force an installation (and overwrite of the current system).

Either way this isn't the best of ideas because you'll soon run into several problems when programs (in specific the ports collection) which will no longer install or which are now at the risk of causing other kinds of errors (note that there's only 1 ports collection, and it assumes that you're using the latest supported version of FreeBSD. So if you happen to run something which relies on a library in the base system which got introduced in version 11 or up then you got yourself a problem).

Downgrading doesn't solve anything, it only postpones your problems for a little while.
note that there's only 1 ports collection, and it assumes that you're using the latest supported version of FreeBSD
Note that both 10.3 and 10.4 are still supported versions. The change regarding the latest minor version being supported is from 11.0 onwards. The 10.x branch is still on the "old" schedule and therefor still supported. Assuming 10.4 will be the last release from the 10 branch it will most likely be supported until Q4 2019.

Downgrading doesn't solve anything
I fully agree with that.
It's currently set to 2018, with a "normal" support schedule (1 year). But this is the regular support schedule. If 10.4 will be last of the 10 branch the support schedule changes to "extended" (2 years) putting the EoL date at around the end of 2019.
Cool, I knew you had said previously towards end of 2018 so I wanted to verify. I'm a big fan of X.4 releases. I'll likely keep using that on most of my machines until 11.x gets 'up there'. I do have 11.1 running on test hardware I borrowed for my home NAS and so far so good. And now I'm off topic.