While adding a Stripe Payment Intents gateway to your account in FlexPay, one of the values you'll need to configure is your Stripe account Id. If you don't have it already at hand, you can follow these 4 steps to get it from the Stripe portal:
1. Log in to your Stripe account https://dashboard.stripe.com/login
2. From the main dashboard, go to Settings.
3. Under Businness settings > Your Business, click on Account Details
4. You'll find your account ID on the top right of the Account settings section.