Flat Fee Shipping allows you to define shipping costs per individual item. This means that regardless of the number of items your customer purchases, the shipping cost will be calculated per item.
For example, let's say you sell a product with flat fee shipping rate $2. Your customer decides to buy 5 items of that product. The total shipping costs he will be paying you is 5 items x $2 per item = $10 total shipping costs.
You can setup unlimited flat fee shipping options and since this is an account level configuration, you will be able to use it for any of the products on any of your store builders.
Within the flat fee shipping type, you can set pre-configured shipping rates defined by delivery date range and price that is set by the store owner. The user can have up to 3 shipping options per zone. Those options consist of Standard, Expedited and Premium.
1. Access the Shipping tile from your store builder dashboard or from the left nav panel
2. From the Shipping dashboard, select + Add shipping class and give the shipping class an internal name, like Flat Fee for example. Save & Start adding shipping zones.
3. Now you are able to add unlimited zones for the shipping class that was just created by selecting the + Add Zone button
4. Enter a zone name and select Save zone 
5. Select the areas to be included in your zone. For certain countries, you can select multiple states or regions. In this example, we select United States and 3 states: Texas, Alaska, and Kansas and select Next
6. Flat fee is the default choice presented in the Shipping Cost Type dropdown; you can choose up to 3 pre-configured services: Standard, Expedited and Premium. You can give them each an estimated delivery range and each shipping costs. The preconfigured services here that are set will then be presented to your customers as they are going through the check out process. 
7. From the shipping class page, you can see all the zones that are created for that class. Here, we have the Local Flat Fee example we just created along with the rate costs at a glance. You can edit, clone and delete this zone from here as well. 
8. Once you have assigned this shipping class and zone to a particular product, this is what it will look like for the store visitors on the front end of your store when they are selecting shipping method 
Please contact our customer support at [email protected] or by simply clicking the chat icon in the bottom right corner of the screen if you have any questions or issues