A thin layer of Apoxie Sculpt clay was applied to the wood staircase. The area where the cornerstones would be installed was left bare wood.
When the stone work was finished on the staircases I used Zap a Gap instant glue to attach the cornerstones. I added more Apoxie Sculpt clay around the cornerstone to help blend it in with the rest of the stonework.
When everything had cured overnight I took the staircase outside and base coated it with grey auto body primer.