Hi, I've been playing badminton for about two and a half years. I've never gotten training so I understand that my forehand form isn't spectacular. I've watched videos of professional swings and after their swings, their arm follows through across their body to their non-hitting side of their body.
The problem with me is that after pronating my forearm for the swing, the momentum of my swing is travelling down, rather than across my body. When I try to follow-through across my body, I feel like I'm slicing the shuttle and not hitting it squarely. So I am a bit confused as to how professional players hit the bird squarely, but still follow-through their arm smoothly across their body. Is there some kind of problem with my technique?
Actually, your technique is correct. The follow-through should initially be in the same direction as you hit the shuttle. After this, the arm is allowed to naturally relax, and the follow-through continues across the body.
If you watch professional players in slow-motion video, you will see this happen. It's a subtle distinction but an important one.
If the whole follow-through is across the body, then you will get exactly the problem described: slicing or mishitting the shuttle.