How to customize the button?

I’m hoping to customize the accessibility icon in the bottom corner so it’s just the icon without the button/box shadow around it, like this:

https://drive.google.com/file/d/1tGiQfgSlRkZNyoge4yae00o2vmjPVe1U/view?usp=share_link

Is this at all possible without losing the box shadow from around the accessibility settings too? And would it be possible to give the icon in the bottom corner a transparent background?

Thanks so much! 🙂