Openssl commands:

openssl genrsa -out self-ssl.key
openssl req -new -key self-ssl.key -out self-ssl.csr -config csr.conf
openssl x509 -req -days 365 -in self-ssl.csr -signkey self-ssl.key -out self-ssl.crt -extensions req_ext -extfile csr.conf

Sign from Root CA: openssl x509 -req -days 365 -extensions req_ext -extfile csr.conf -CA RootCA.crt -CAkey RootCA.key -in self-ssl.csr -out self-ssl.crt