I'm using a third-party payment method. Their API provides an iFrame, which we can place anywhere we want.
This is the supposed flow for checkout we that method:
On Shopify's checkout page, upon selection of that particular payment method. A modal window (iframe) will open over the page and all the process + payment will be handled in the modal window. Once all the steps are completed, the modal will be closed and we'll complete the order.
Is there any possibility to create this process without Shopify Plus or Shopify Plus is a hard requirement to achieve this functionality?