It is possible to automatically add a product to the shopping cart after it is created using Odoo v12 e-commerce. To do this, you will need to create a custom website form and enable the "Add Product to Cart Automatically" option in the Form Editor. Once enabled, the product will be added to the customer's cart automatically when they hit the submit button. You can also set up a redirect URL once the product is added to the cart so that the customer is sent to the Payment page.