I have installed a pair of fog lights in my stock bumper.
I cut holes in the bumper which are the same size as the the face of these lights. The lights couldn't just be mounted directly to the bottom of the bumper, the mounting surfaces needed to be raised.
They are mounted to the bottom of the bumper by using a longer bolt and multiple washers to raise the mounting surface so the light fits into the holes cut.
installed
However, the output of these fog lights does not compare to the output of the 6" long range lights.
...On the same topic, I also installed a pair of fogs inside the rear bumper as aux backup lights. I really like having aux back up lights.
They are mounted similarly by first cutting a hole in the bumper. These are different fog lights then I used in the front. They are similar to these,
To mount them, I unscrewed both screws on the lamp face, drilled holes into the bumper, and the screwed those screws back into the lamp effectively "sandwiching" the light into the bumper.