Using a magnetized stem to demonstrate the potential launch angle that your ball is going to have; you will notice that on chipping downhill even though the hands are forward and the weight is forward trying to send the club down the hill through the ball the launch angle of your right knee should be slightly flexed and forward. The sole of the club should skip and deflect down the slope.

Naturally allow gravity to bring your body down in the direction of the slope.  Do not try to set your shoulders with the slope. If you try to level your shoulder with the slope you are going to throw yourself off balance and cause the axis of your swing to be in the position where it is going to cut across the ball. Make sure that the weight is positioned solidly in the downhill leg with hands naturally forward and your head slightly behind the ball. Your right foot is slack and there is no weight in it. On the back swing, push back with your left shoulder and move it down and under while maintaining its rotation with your forward spine angle. Let your shoulders fall naturally into the ball.  Do not keep your hips and head still and never shift the weight from one leg to another, the weight should always remain downhill. It is also important to hold the finish with your right upper arm.

Using the same principle in chipping downhill you can also chip the ball when it is positioned below the feet only that you have to sit a little bit more on the heels.

You are not using the hands and arms, you are using the shoulders to push a lower case triangular unit back and then let that unit fall through the golf ball. You hit the chip with just the weight of the arms, shoulders and club unit. If you try to pull back with the arms with your body not following, you will push through with the arms and yip the ball.