Auto-opt in for Subscribe by Email

Hello support! I'm looking to use auto-opt in instead of the default double opt in. I found this setting under the widget settings which works great. However I am also using a custom subscribe page with the following code:
subscribe-by-email-form
(brackets omitted to prevent the code from rendering here)

Is there some way to adjust this line so users subscribing through it will auto-opt in? Thanks in advance.

-Brady