WARNING: First of all disconnect an amp from the power outlet!
Please be careful - Tube amps can hold a serious amount of electrical charge that can cause injuries or even death. Avoid touching any wires or contacts with your bare hands or instruments that have no reliable insulation.
Now it's time to remove the nuts on the input jacks and our broken volume pot - I used pliers to do that, but it is advisable to use a small adjustable wrench, combination wrench, or socket in order to avoid any unwanted scratches or damage.
Next let's remove the volume knob - you'll need a flat 2.5 bit for that. Carefully insert the bit into the hole on the rear side of the knob to undo a tiny screw inside of it.
That's it - chassis is free 👍.
Hint: use a plastic tray or a magnetic mat to safely store all of those screws and nuts. You can even write where all those parts come from.