I took the painted lath and cut one end on a 45 degree angle.
Mistakes made were using lath JUST big enough without any wiggle room. One corner had to be butted instead of beveled. The bevels didn't meet like the would if I had constructed the frame first and then seated it around the piece. I was left with poorly made corners. I used black "Gorilla" tape to mask the joints which were VERY evident. It might not look perfect but it was a massive improvement and not that visible from a distance. The gaps WERE very visible when looking head on.
And a bonus picture of my backyard. Sunrise over the church. The plastic on the ground will be a garden my neighbor is planting to grow food for our town food pantry. I just donated the garden plot.