Hey Rodders 61,
My understanding is that either one is correct. I have seen pictures of the various 109 models with the slats extended sitting on the ground just after landing. The slats were free moving and they extended or stowed based on aerodynamic forces when in flight - the pilot had no control over them other than by changing speed and/or AOA. Bumping along on the ground after landing would usually cause them to extend if they were not already.
Operationally, I believe it was standard practice for the pilots and/or ground crew to stow the slats when the aircraft was being ground handled or while parked - in order to help reduce the chance of accidental damage. But the preflight check included making sure the slats could move freely, so they would usually be extended in the photos of the aircraft just before Taxi and TO.