how to make boarders for projection mapping

[vj8k3]

Any tips or trick for projection mapping the boarders of surfaces? I want to be able to change the boarders of these triangles to different clips then the center. I think it will add more visual complexity. I was also going to paint them silver rather then gray to distinguish the difference.

I also wanted to switch in-between having the image duplicated to it being the 4 triangles cut out.

https://www.youtube.com/shorts/rXL_SrpQBX4

any ideas?
thanks

[Zoltán]

Like a Slice outline?
You can make one with Wire.