The process I use is:
Create a plane that has the same size as the image.
Then uv map the plane.
Create a material which includes the image and apply the material to the plane.
The flip image commands in the material settings are buggy when you reopen your scene so don’t use those. If the image is upside down then re uvmap and check the flip u or v options under the uvmapping options.
Wow…that’s a lot of work just to get a background image to model against.
Can’t you just flip/rotate the plane manually?