Booting time very slow after restoring Fusion Drive

Hello,

I recently restored my 2TB Fusion Drive because Windows had messed it all up when I tried to restore it from a System Image (please see here: Recover Windows 10 from System Image under Boot Camp). Basically, the HDD and SSD got separated and I rebuilt the Logical Volume Group and all. Now the booting times in the OS X partition are pretty slow, so is generally using it for the first minutes - kind of like Windows booting up.

My questions:

1. Should I have restored OS X to the SSD part of the Fusion Drive? Or was I right to assume I should install it on the HDD part and the Fusion Drive would "do its magic" and, in time, transfer booting-relevant files to it on its own?

2. Would re-installing/restoring OS X on the SSD part resolve the issue?

Thank you,

Bruncky