Fixing stainless steel fire surround

I'd suggest stainless machine screws, to nuts behind the slate. Countersunk head torx screws maybe.

You really should be able to get little torx-plugs, that press into the screws, but I don't think you can.

I should have mentioned that the fire and surround are in place, I am changing the edge strip. I cannot get to the rear of the slate.

I have a redundant stainless surround that you could have foc. I cant say what its measurements are -as its outside and I am currently in my jamas. You can contact me via my ws -

No, fire cement wouldn't hold (or at bes would provide a marginal bond). It's great for many things, but not as an adhesive.

I'd use high temperature silicone:

I live on a farm and we like our fires HOT. Didnt think any silicone would hold. In my past I used to mess with proper rocket motors, and we always used ordinay Evostick to bond the propellant to the case. It may go black but never gives up holding even at really high temperatures. Still holding one year later...