OK, so when I started out, my ex-coach told me to hit the serve with my regular forehand at that time, which was a semi-western. So it was pretty easy for me to get the hang of hitting flat serves. Then I changed coaches and he's teaching me the slice serve right now but when I am hitting without him, this guy who I hit with told me to learn the flat serve. So I tried, using the continental grip. But I keep hitting slice serves, or at least half-flat half-slice. It really frustrates me because no matter how hard I try, I still hit it with slice. I think this is because of the natural stroke of the continental grip is slice and not flat. Any advice on how to hit flat serves? Like can anyone tell me where to throw the ball and how to stroke the ball at the contact point?