It is essential to create a bootable OS. In the event of a crash where you can't use the OS recovery, you will need this.
Initially its a little time consuming but it will save you loads of time in the future.
**Important** Ensure you have a backup of your data. TimeMachine would suffice.
The best Youtube recommendation would be from Anson Alexander " https://www.youtube.com/watch?v=n_1dsri56MU "
This is Summary of the Video. Please watch the video first.