How to add Calendly embed code within a List Details block
First of all, you need to get your Calendly embed code, as described here. Further on, create a corresponding field in your Airtable table that you're using for the List Details block. In the example shown below, we've created a Single line text field named "Calendly" and added the embed code to one of the rows.
Adding embed code to Airtable
Next, you'll need to add an Embed type field to your List Details block and link the "Calendly" field from Airtable.
Adding the embed field
That's it. Now the Calendly embed will start appearing on the list item as shown below.