So at the bottom of your crontab (vim crontab -e), just add these two lines to run your command - for example, to run twice a day at 2am and again at 2pm.
0 2 * * * redis-cli del Allblocks
0 14 * * * redis-cli del Allblocks
Just to test out, run this in a crontab and see how it work.
* * * * * redis-cli info clients >> ~/clients_info.txt
So no need to write a script. You can run your command directly in your crontab.