There are 3 options for integrating Deadline Funnel with a Squarespace optin page:
Integrate Deadline Funnel with one of our email service providers via API:
Deadline Funnel integrates with these ESPs via API
Add an optin form from your email service provider on your SquareSpace optin page and then use the Deadline Funnel Optin Form Integration
Integrate using an invisible pixel on your thank you page as explained here
You can find instructions on how to add a countdown timer to your Squarespace page here: How to Add a Countdown to Squarespace
If you have any questions, please let us know at firstname.lastname@example.org.