You can have a button with a fixed position (maybe in a distinct section so that you can reuse it through your app). This way, the button will always be positioned relative to the screen. On click you can have a workflow to display/hide the component that holds the chat.
Thanks @jptrinh
I was able to place the button on fixed length and height.
But when I click to open that container
It basically pushes my button out of screen.