Fermzilla bottom valve open or shut during fermentation?

I am about to set about my first pressure fermented lager, and will be using a Fermzilla V3.

This has a large valve at the base of the conical pressure vessel leading into a small jar that can be shut off and removed.

When initially filling and starting the fermentation should I have this valve open or shut? (i.e. should the bottom chamber be full and open during fermentation)