Is it possible to change the slope of the forehead? Female with a 'domed' forehead wants a 'sloping' forehead (Photo)

I think you are headed for trouble.  Some types of trouble are not fixable.  The problem is that if you knock on enough doors, someone will try this for you.  I do not think what you are asking for can be accomplished without enduring the very real risk of being permanently damaged by your potential surgery.

Your forehead bossing can be reduced but not to the degree of slope change that you have shown in your model images. The frontal bone simply is thick enough to allow for that degree of change. If you are going to use hair transplants for hairline lowering that should be done after the forehead reduction. You will need the hair transplants to potential improve or hide the pretrichial hairline incision. Only if you are doing hairline lowering by scalp advancement can both it and forehead reduction be done at the same time.