How to make an appointment letter and payslip for a freelancer or consultant on a project?

How to make an appointment letter and payslip for a freelancer or consultant on a project who is not a salaried employee with a company.

Dear Swish111,
The salary slips are issued to the paid employees only. Consultants or freelancers raise their invoice for the service(s) they provide. Payments are made after checking the correctness of the invoice as per the contract agreement.
The role of the HOD is limited to checking the correctness of the invoice and forwarding it to the accounts department for payment.
Thanks,
Dinesh Divekar