Simply replace the unfilled areas such as "" and "[date]" with your information.
This letter is formal notice that your employment with [name of organization] is terminated effective immediately due to insubordination. The following are [transgressions/incidents] that have forced us to terminate you:
1) [1st transgression/incident]
2) [2nd transgression/incident]
3) [3rd transgression/incident]
4) [4th transgression/incident]
Your final cheque will be ready for pickup on [date].