Stretch and squeeze for a wider chest.
Hold that soft elbow bend the whole time, this is a hug, not a press.
The fly does the one thing pressing cannot, it isolates the chest's true function, sweeping the arms together across the body, without the triceps taking a share. The wide arc puts the pecs under load in a deep stretch at the bottom, which is the position research and gym experience agree drives growth, while the front delts help steer the path. It earns its place as the isolation move that finishes what pressing starts.
Presses first, they let you load the chest heaviest. Flyes then add what presses miss, a deeper stretch and pure chest isolation with no triceps involvement. In most programmes flyes come after the pressing is done.
Until you feel a strong stretch across the chest, usually with the elbows around torso level. Deeper than that adds shoulder strain, not chest growth. The stretch position is the money, so lower slowly into it.
The long lever, your almost-straight arms, multiplies the load on the chest and shoulders. Heavy flyes force the elbows to bend and turn into a sloppy press. Stay lighter, keep the fixed elbow bend, and let the stretch do the work.
