How to get an object to fill 3/4th of the screen.

Hi, I'm pretty new to Unity and coding in general and I've run into a bit of a problem. I currently have a GUI menu for the player on the right 1/4th of the screen and am currently trying to get a plane that I intend to use as the game board to fill the remaining part of the screen. I assign the plane to the board object, but its scale remains 1 regardless. I also can't figure out how to get it to default to the top left of the screen. I am trying to use the following code:

 void screenPos()
 {
     Vector3 temp = transform.position;
     temp.x = -(board.transform.localScale.x/2);
     board.transform.position = temp;
 }
     
 void fitScreen()
 {
     Vector3 temp = transform.localScale;
     temp.x = (Screen.width)/4;
     board.transform.localScale = temp;
 }

I figured that I would be able to use the same method that I used to get the GUI to show up on the right 1/4th of the screen, but when I try to use the methods above it returns the values for Screen.width/4 as 229 while using the Standalone View window. Any help would be appreciated, I'm pretty well stumped on what to do.