Need custom form built on website with output to google sheets (based on but not using a completed google form)

I need a google form coded into my website, not a google form linked or embedded, the same workflow with output to a google sheet but run purely on my website hosted by Squarespace. I just want the same series of custom fields all on the same page that clients can complete and submit which then populates a google sheet with the data to be picked up by another app from there.