Create a platform with your arms. The platform is the area between both your wrists and elbows which is the "sweet spot" for hitting the ball. To create your platform, the most important thing you need to do is to clasp your hands together correctly while holding your arms straight in front of you, slightly below your waist, with your shoulders arched. Clasp your hands in front of you, with your thumbs together, side-by-side. Don't lace your fingers together, for this will make you lose control of the ball.
You can either make a fist with one hand and wrap the other around it (the ball method), or you can bend one thumb down to its palm, and rest it on the other hand (the cup method), thus cupping it with the other hand.
If you're using the cup method, then your thumbs should be parallel with each other, and your four fingers on each hand will be parallel with each other as well.