Free throws are the easiest shot in the game and the most missed under pressure. Easy isn’t the same as calm.

Difficulty and pressure are two separate things, and only one of them is about the task. A simple action performed while everyone watches becomes a different action, since your attention moves from the motion to its meaning. This is why people fumble things they have done correctly a thousand times.

Practice the easy thing under something like real conditions, with noise, with someone watching, with a consequence attached. Build a small routine you run every time so your body has something to follow. The aim is not to feel no pressure, only to have somewhere to put your attention when it arrives.