"Very nice," your devilish chastiser comments approvingly, gently hooking all eight fingers inside the back waistband of your light blue sweat pants, and then worming them into your underwear as well:
"Now let's give you some southern exposure, sweetie..."
With a quick continuous movement, she smoothly pulls your sweat bottoms and your underwear both down to your lower thighs to expose your twin bottom cheeks. Your spankings are of course "bare bottom" for maximal effectiveness.
In addition it's very humiliating to have your stiff cock exposed during a spanking.