It doesn't have to be a superhero/wonderwomen type pose. The idea is high power poses, poses that make you seem like you are the boss and you know what you're doing.
I'm an officer of a couple clubs in my school, did a lot of presentations in class, did multiple speeches in front of thousands of people and I do utilize this trick a lot. I believe the original source for this is Amy Cuddy's TED talk on this. High power poses scientifically reduce the stress hormone in our bodies - cortisol.
I like to use a desk and an office type swivel chair. You can put your hands wide on the desk/table with your feet just as wide. Lean forward and pretend you're like talking to people at a conference table. Or you can put your arms behind your head, lean back in your chair and put your feet on the desk.
Doing my freshmen year of high school this year was the first time I had to do a lot of public speaking and I fell into it quite quickly. It became very easy after a while, just pretended that I was an awesome power speaker. Visualizing in your head giving a speech in front of thousands of people can be beneficial.
My first opportunity is when I ran for president which was 2 weeks into the school year. I utilized the power posing technique and did okay. My speech was about 3 minutes long with 4 paragraphs. I didn't stutter or stumble over any word except the last sentence (my campaign slogan) because... I bit my tongue.
During high stress times like these, you completely forget about your bodily actions. People like to sway their bodies back and forth, lift their feet up and down, play with their bracelet/ring/accessories, swallow a lot, etc.
My tip is just to slow down..take it easy and don't be afraid to take pauses. Pauses make your speech sound well thought out and articulated, instead of filling the silences with ummms or uhhs. It might feel extremely awkward and pausing for 2 seconds might feel like 15 seconds. But it'll seem natural to the audience if you don't pause for more than 4-5 seconds. During the pauses though, don't look nervous, just look around at the audience and try to make eye contact with everyone in the room. During my presidential speech, I was facing a bleacher full of kids stretching across an entire gymnasium. I looked through the entire gymnasium during my speech, trying to make eye contact with everyone and connect with them. During those pauses, be aware of your body movements and you're not having any nervous tics.