What did you already try and didn't work? Your 'please provide complete explanation of steps' sounds like you are looking for us to do your job for you. 

Also: validate your requirements. Do you really accept a requirement of sending an email if 10% of the SLA has elapsed? If you have 10 days to resolve something, the manager is being bothered with it after day one. 
To help you start: check on the existing 'SLA notification and escalation' flow. It is configured to do the same after 50%. You can adjust it to your requirements.