Add-on products let you sell products online when clients are booking their appointment. However, if you need to sell products online without an appointment to ship to clients, you can setup an online products booking flow. Be sure go to settings>features>packages>toggle on>save.
Pro tip: If you want to sell products but then have them pick them up, just create a service product pickup for $0 and they can book an appointment to pickup their products.
To setup products for online sales, head to settings>packages. Label the package as the product name and set the price you want clients to pay for the product. You can add other information like a description as well. Be sure Show online is toggled on. For the Apply package field, select (or create) a service that doesn't show online so clients can't book the service.
Pro Tip: If you want to ship the items, make a form with a long text field that asks for their address and attach it to that package so you can get their address as well.
Head to settings>services and tap + on the top right. Create a new service and any title is fine. The price is $0 and be sure to toggle off Show online.
Save your service and head to settings>packages. Tap the + on the top right to create a new package. Title the package the name of the product. Set the price as the price you want clients to pay for the product. Then, tap Apply to>to select items>tap on the new service you created so it's the only service to which it applies. Be sure show online is toggled on and save your changes.
Now clients can purchase the package right from online booking to buy the product without needing an appointment.
Pro tip: Turn on categories and make a product category just for packages you have setup for products.