A poppet can be as simple or as elaborate as you like — it all depends on how much time and effort you want to put into it. You can construct one out of just about any material — cloth, clay, wood, wax. Use your imagination! In some magical traditions, it’s believed that the more work you put into it, and the more complex it is, the stronger your link will be to your goal. Because a poppet is a device for sympathetic magic, all of its components will be symbols of what it is you hope to achieve.
You can do your poppet-making as part of the working itself, or it can be made ahead of time so you can use the poppet later on. Which method you choose is really up to you.