You can use our Signature collection automation for this! Here's how:
Select the table used by your Airtable form
Choose the attachment field that should hold the signatures.
Copy and paste the Signature URL to your Airtable Form's 'Redirect to URL' setting.
Now, your users will be redirected to our signature page after submitting the Airtable form. Once they sign, the signature will be stored in the attachment field you configured!