For those using the Stripe gateway it is possible to configure flat rate shipping that will override any shipping costs on individual products and allow for a single shipping price for an entire shopping cart.

You can configure flat rate shipping for multiple currencies, these settings will override any individual shipping rates in a customers shopping cart. A currency specific flat rate shipping setting will only apply to shopping carts that have items with the same currency. If you only support a single currency in your online store then you only need to configure a single flat rate shipping setting.
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From your Home dashboard, select E-Commerce.

Next, click on the Store settings.

If you configure more than one flat rate shipping setting per currency then the customer will be able to choose which setting during the checkout process. e.g National Shipping or International Shipping. This is useful if you need to provide different shipping costs depending on the customer. 

Flat rate shipping will automatically be applied to a customers cart and override any other shipping costs against individual products. If you want individual cart item shipping to be applied then you will need to leave flat rate shipping turned off.