This is a relatively easy shot to reproduce - if you can get a dog to sit still.
The light is from a late-day sun (warm color balance). The background is simply a green field. The problem of course is getting the dog to look in one direction long enough to capture the shot as the depth of field at 300mm, f/2.8 and this short focus distance is not tolerant of any movement.
Camera and Lens Settings
300mm f/2.8 1/1000s
3744 x 5616px