You've got this.
The kids are on the rug, and you ask them, "Think of something flat and move it behind you as you listen to the music."
The music ends, and everyone is back on the rug.
Then you ask everyone, "What were you thinking about as you listened to the music?"
So far, so good.
Now, what will the children say? The graphic below gives you an idea of what your kids may say, and it's important to note that there will be similar responses, which is okay. If you think about this with STEM in mind, the constant is, in this example, flat, and the variable is the child's thought.
Few things are perfectly flat. So, compared to something else, all of these answers are plausible.
However, "tire" was not an expected idea but logical in the context of traveling by car. I find that these unexpected ideas turn into wonderful conversations.
At first, ask and listen. Later on, you may want to write their thoughts on paper or a whiteboard.
I will create a Podcast explaining how to work with an idea. Look for Episode 105: Think of something flat.