Passing parameter to process (when called process action with process start form) as Embedded Interfaces on External (Non-Appian) site

No answers on any of these posts:

Do we know if there is any recommended way of passing the process model parameters when exposing the process with process start form as Embedded Interfaces?

• community.appian.com/.../passing-input-parameters-to-embedded-interface
• https://community.appian.com/discussions/f/general/12171/using-embedded-actions-process-start-forms

(Not looking for any webAPI based approach, as there is a risk of race condition always, hence said any "recommended" way?)

Thanks!