Steven
The frame looks great.
Can’t see any gaps in it miters.
I did a 4’ X 4’ frame for a friend’s map once.
Used Mahogany.
On the back side, I manually carved some rebates for metal L- brackets just in case.
I did the trim around our windows at the farm house. The biggest one is roughly 6’ X 10’.
It’s black walnut and it’s just glued mitered corners built just like a picture frame.
The only thing is they are so large, I did the glue up setting on the floor with a Merle band clamp.
After the glue dried, I basically snapped them into place around each window.
They were done and installed about 16 years ago and they’re still perfect!