Your providers' bank account need to be located in one of the countries listed here.
The bank account can be in any of these countries, regardless of where the admin Stripe account is located. If the bank account's currency is different from the currency of the marketplace, conversion fees may apply.
This will automatically create a Custom (previously named Managed) Account in your Stripe admin account. However, sellers don't have to worry about this. They don't have to create an account at Stripe. All this is done automatically.