Pre-Checkout Offer is displayed on the Checkout page when the visitor or user clicks on the Place Order button.
This helps you to Offer an product before even starting the checkout process.
How to Setup Pre-Checkout Upsell in CartFlows?
Navigate to CartFlows ( WordPress Dashboard ) > Flows > your_flow > Edit the Checkout Page -> Navigate to Checkout Offer tab -> enable the Enable Checkout Offer option > select your product under Select Product option.
You can also change the other options/setting in the checkout offer below for further customizations.
Visit the Checkout Page on the frontend. After filling the details there, now when you click on Proceed to Checkout an offer popup will be displayed.
Like the following screenshot –
Note: It will work with almost all WooCommerce payment gateways.