give me an idea how you would lay it out on paper
Draw a rectangle representing the frame.
In side that rectangle draw other rectangles where you want to have a button or a text area or some other components. Continue until you have all the components you need and they're positioned where you want them.
The layout would depend on the application. Say you are reading a file and writing to another file, you'd need two text fields to put the paths in and two choose buttons to go to a file chooser to select a file for that text field. Then a Compute or Doit button underneath. Perhaps a Stop button if you needed to stop the background task and maybe a Cancel button. The buttons could be in a panel beneath the text fields.