How to set new browser window to open behind taskbar

I am trying to figure out how to make new popunder window to appear behind the windows taskbar or behind the clock. I think for it to work the code has to be understand the visitors current screenX and screenY but I canĀ“t figure it out.

So far I can make the popup open right above the clock, but not behind it using this code from w2schools: https://www.w3schools.com/jsref/tryit.asp?filename=tryjsref_win_screenx2

Thank you for reading and hopefully you will have some ideas how to tackle this.