This is actually a good question, because, it seems, no two people (even very good players), have the same concepts of what is happening when they put various kinds of spin on the ball.
To be more realistic, imagine the ball, exactly as it is-- a sphere, and the racket face, what it is-- a flat plane.
And to further simplify, imagine you are hitting a topspin forehand groundstroke right in your comfort zone.
Imagine you want to hit the ball about three feet above the net straight over the middle of the net. Imagine the arc the ball must take and the forward momentum you must gernerate to place it deep near the baseline.
What part of the ball do you actually hit. OK, think about it. Your racket is pretty much perpendicular to the court surface and your racket strikes the ball traveling from low to high at (say) a 25 or 30 degree angle.
No matter what the angle of your low to high followthrough, if your racket face is vertical, then you are basically hitting it dead center (where it bulges out most)-- and it is the action of the low to high follow through that adds the spin.
OK, now just tilt the whole concept up over your head and imaging the same action 90 degrees on it's side. The ball is still a sphere and your racket face still a flat plane. With some very minor adjustment because you are hitting the ball from about 10' up, the concept is basically the same. The ball is a sphere, The flat planeof the racket face strikes the part that bulges out opposite a line drawn straight through the ball toward the toward your target and the spin is still created by the racket following an angled path through the ball. For a right-hander that would be from left to right.
Now, just as for a groundstoke (imagine it in your comfort zone), you can hit the ball with various amounts of topspin, slice, or even sidespin without having to change the position of the ball, you can (to an extent) do much the same thing for your serve.
Personally, I move the ball toss fairly little to produce the different types of serves/spins. What I alter is the racket path through the ball.
That may not work for everyone, especially if your are just starting out, As suggested by some of the others, above, it may help you to hit through the ball with the proper angled followthrough by moving your toss a bit to the left, right, forward or back- depending on the shot you are trying to create.