To have a good finish position at the foul line, it all starts from the beginning. It starts off with your stance, your timing, and your allowing yourself to go forward and creating good balance and leverage at the end. To have a proper finish position, you have to have not only the right footwork, but you have to have the ball in the right position and also your perspective of the lane; your targeting is going to also reflect on that too. So by creating a good stance and good starting position, it's going to translate into your finish position.
When you have the proper start of your approach, you're going to be able to get into that finish position, transfer your weight into your left leg, into your swing. When you get to that foul line, you want to not only have your head steady, your back angled towards the lane, but also your head over your knee. When you get that position, you're going to be solid; you're going to be like a basketball player posting a shot and shooting a hoop. When you get the ball into motion and you're transferring weight, all that weight is transferred forward, and you're going to be solid. It's also going to allow your feet to be not only flat on the lane and on the approach but your right leg (if you're right-handed) will kick out and still be on the floor. If your leg does a kick up in the air, that means you're a little too high, or you're maybe throwing the ball too hard. So you have to remember to keep your feet centered and going forward towards the lane.
Having the proper finish position all starts at the beginning. By having good position, stance, good timing, good footwork, you're going to create a solid finish position. Just by doing that, it will make you more consistent, a stronger bowler, and also creates an area in a lane to be able to score higher.