Hello friends!
A while ago (pre covid / 'the before times'), I fashioned a ceramic mosaic on some 800x1200x5mm MDF board. It was my first project of the kind and I didn't really think far ahead in terms of how I would like to eventually display it. Initially I had planned to mount it directly on the wall, but as the project neared completion I realised just how heavy it was and how that was likely to be infeasible. With all the tiles, grouting etc, the piece weighs just shy of 21kg.

I have recently moved into a home of my own and I would very much like to display it on my wall. Before the project was completed, I screwed&glued the MDF board onto a basic backing frame built from 30x70mm pine beams, per the diagram below.
Backing frame dimensions
I am seeking some advice on how best to mount this to my wall (double brick and plaster), as my skills in this area are quite novice. From my readings, I have been contemplating fashioning some French Cleats from the same format pine timber, and attaching them to the underside of the top and 'middle' beams. My concerns are:
- I am not sure if this sort of mechanism is capable of supporting such weights (>20kg)
- I am not sure how structurally sound any cleat will be if I try to attach it to the MDF board. I cannot use long screws which will go into the mosaic itself, and due to the low width of the board I don't know if there will be enough 'grab' from screws which only penetrate that far. I am considering instead mounting the top of the cleat into the beams so that supporting screws run up/down (from direction of hanging) but I don't know if this will impact on the integrity of the cleat (ie, holes in the angled surface of the cleat)

- Most examples I have seen online have been for these cleats to be installed into timber or drywall - is it appropriate to install cleats onto a brick wall?
I'd be very grateful for any advice you could provide, or for some alternatives which I should consider capable of hanging heavy artwork like this?
Thanks very much!
Luke