How to draw a nested Jpanel through the paint method in Java Swing?

Question

Java

I need to make a small app where some background will have multiple dials with changing values.
I can arrange these dials using GridBagLayout, but I do not know how to make a background image for the panel in this case.
I can also draw this background image manually through the paint method, but in this case I don’t know how to draw these dials (they are JPanel).
In extreme cases, you can draw everything in one paint method, but it will be just monstrous