Things on this page are fragmentary and immature notes/thoughts of the author. Please read with your own judgement!

https://stackoverflow.com/questions/10175812/how-to-create-a-self-signed-certificate-with-openssl

https://www.linode.com/docs/security/ssl/create-a-self-signed-tls-certificate/

https://www.ibm.com/support/knowledgecenter/en/SSWHYP_4.0.0/com.ibm.apimgmt.cmc.doc/task_apionprem_gernerate_self_signed_openSSL.html

Note: You can get free SSL from Let's Encrypt.