That fork crown looks exactly the same as my 1" fork crown/steerer.
I think that looks like a crown race collar.
So put the steerer into the frok crown and tighten it up, then slide the crown race collar down the steerer.
The crown race from your headset then fits on over the crown race collar.
I've only ever used a crown race collar on a 1"1/8th steerer though, I've not yet fitted the 1" steerer RC35's so couldn't say 100% if you need the crown race collar.