Pressure into flow... Welcoming, even looking for higher stakes speaking opportunities is a great way to open the door to flow speeches. Finding flow does take practice and IME speaking off the cuff, under pressure, opens the opportunity to find flow.
I remember when I first took my first class in public speaking. We played games online. It was easy to get access to. It was easy to put the reps in. It was easy to get lots of opportunities. Even at only a minute or a minute and a half or two minutes at a time, that was all extemporaneous. It was all impromptu. It was all: "Here's a subject — now make a speech." Seemingly super hard, but then the time frames are crunched. Then they're trying to speed you up. Then they're trying to slow you down. There's all this pressure...
But that pressure that unlocks the door. If you let it flow, then it gets easy. You're not even thinking about confidence at that point, because you're in flow you're in.
The best place there is to give a speech for both you and the audience.