Great question, We get so many drug questions, this is a nice change of pace, so than you! haha. I always start guys with slow steady state and if that is enough, we will stick with it. I have gotten to low low single digit body fat never doing more than walking on a treadmill. Start with 30 min, incline of 3, heart rate at 120-125 BPM. The diet should be the main thing that generates fat loss. From there, add small amounts of cardio as you go to keep the calorie deficit going up. The best time to do your cardio for fat loss, is first thing in the AM, fasted. The next best time is post workout
If my client isn't responding the way we want, or if they aren't losing fat at the rate we need to make a deadline, we may move to short sessions of HIIT.
So start with 30 min, 5 days of SSS cardio on the treadmill.