Although zentara's solution of using place may work, much depends on how complex and intricate your application will become. The disadvantage of place is that it does very little of the calculation and automatic allocation that the other geometry managers do. Granted, relative x and y do what you want here.

Perhaps you should consider using grid, if your application is laid out in rows and columns like an Excel spreadsheet or a HTML table. In this case, setting gridColumnconfigure($_, -weight => 1) for all columns and gridRowconfigure($_, -weight => 1) for all rows, will give you a grid which will give proportionally equal space, and resize properly when you resize the parent window. For an example of this, have a look at the RPN calculator example here.

For more sophisticated layouts with percentage allocation, look at form, though I have never had need to use it.

Hope this helps