So you can see how the FormSpammerTrap contact form works on a WP site, I changed the Contact Form on https://www.cellarweb.com (my ‘company’ site, runs on WP) to use FormSpammerTrap (FST) via a shortcode on a page.
All I had to do is copy the theme’s page template into a new file, change the template name (so I could find it), and add four commands at the top of the template file. Uploaded the new template file.
Then set up some parameters in the FST functions file (full instructions on how to do that included), mainly to add reCAPTCHA v2 (I already had the keys) and set up the email address. Then uploaded that file.
Changed my existing Contact page to use the new FST shortcode, published it, and that was it. The whole process took about five minutes.
You are welcome to try it out the new contact page on the CellarWeb site. There will be no Contact form spam there.