Tiled coffin keezer lids: attaching the coffin box?

[grahamb]

A question for all you coffin keezers: I'm in the process of building one with a tiled top; 3/4" ply + 1/4 hardibacker as the substrate. I'm not sure how I should be attaching the coffin box to the lid; I can see two options:

1. Attach the coffin box to the plywood first, lay hardibacker and tile around the box
2. Attach the hardibacker to the plywood first, then the box to the hardibacker and into the plywood; tile around the coffin box.

I think option 1 makes the most sense? On the face of it, option 2 seems like the least work, but I'm not sure about screwing through the hardibacker (likely using pocket holes on the inside of the coffin to secure it to the lid.

How have you secured your coffin boxes to tiled lids?