Hi @trebortron
Thanks for reaching out!
Firstly, I apologize for the delayed response.
Wondering if there’s a formula for flat rate shipping cost to be set for orders under a certain value?
Flat Rate Shipping?is a shipping method included in WooCommerce that?allows you define a standard rate per item, per shipping class, or per order.
In the example below, setting the Calculation Type > Per Order?–?charge shipping for the entire order as a whole, the customer with 5 items in their cart would pay $5.25 for shipping and a customer with 1 item in their cart would also pay $5.25 for shipping.

Image Link: https://snipboard.io/WD6J0K.jpg
In your case, since you would like to set a flat rate shipping cost for orders under a certain value, I suggest you check the Advanced Flat Rate Shipping Method for WooCommerce plugin since this could achieve your requirement.
Advanced Flat Rate Shipping for WooCommerce is useful for WooCommerce store owners who want to charge a fixed amount of money or flat rate for shipping products while applying different conditions on the cart.
If you want to try our products, please note we have a 30-day refund policy.
If the product doesn’t work the way you need it or you think another product would work better, we are more than happy to offer a full refund. You can read more about our refund policy on our website here.
Hope this helps!