Adding form field to checkout block

Hi everyone,
I am trying to add a first and last name field to a checkout form. I have seen a lot of questions around adding extra fields to the form but have found no actual solutions.
The problem is that clients that order through the website do not all fill in their last name which I ideally would like to have for shipping purposes. So instead of having just a ‘Full Name’ field i’d like to split that into ‘First’ and ‘Last’ name fields.
Looking forward to your responses.
Cheers,
Dennis