[hardwired]

Code:

import java.awt.*;
import javax.swing.*;

public class Test {
    public static void main(String[] args) {
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setContentPane(getContentPane());
        f.pack();
        f.setLocationRelativeTo(null);
        f.setVisible(true);
    }

    private static JPanel createContentPane() {
        JPanel redPanel = new JPanel();
        redPanel.setBackground(Color.red);
        redPanel.setLocation(10, 10);
        redPanel.setSize(50,50);
        return redPanel;
    }

    private static JPanel getContentPane(){
        // GridLayout tends to ignore the size hints,
        // creates a grid of the available space and
        // tries to size the components to fill the
        // space of the grid cells.
        JPanel mainPanel = new JPanel(new GridLayout(2, 4, 10, 30));
        mainPanel.setPreferredSize(new Dimension(604, 310));

        JPanel tempPanel = new JPanel();
        tempPanel.setBackground(Color.blue);
        tempPanel.setMinimumSize(new Dimension(50, 50));
        tempPanel.setMaximumSize(new Dimension(50, 50));
        tempPanel.setPreferredSize(new Dimension(50, 50));
        mainPanel.add(tempPanel);
        mainPanel.add(createContentPane());
        mainPanel.add(createContentPane());
        mainPanel.add(createContentPane());
        return mainPanel;
    }
}