For a project that must deliver a tangible product, using phases might not be the best way to divide the production process. Work on the different sub-components can take place concurrently. In this case, it might make sense to structure work by major deliverables
It's important that the WBS accurately represent all the work that must go into a project. So the second level must also include the work that goes into project management, which is central for any project. Project management breaks down into activities such as planning, coordinating meetings, and administration.
You can structure a WBS in different ways. What's important is that you make it clear what the major areas of work are and how deliverable components will come together to ensure the successful completion of the project. Typically, it makes sense to include from four to six levels of decomposition. This is to ensure the WBS is not overly complex and remains manageable. Remember, your goal is to get a clear view of all the work that must go into the project. So simplicity and clarity are key.