Since the locking tabs extend through the PCB, it's helpful to place the PCB on the edge of something like a cardboard box while soldering so that the locking tabs are free to extend below the PCB, allowing the potentiometer to be completely flush with the PCB.

Now is a good time to test that the volume knob and microphone still work before reassembling the case.

If flux was used during the soldering process, it's a good idea to clean it off using isopropyl alcohol or a circuit-friendly cleaning solution before reassembly.