FYI - I am trying to do this on an android smartphone (Xiaomi Redmi Note 9 Pro).If you would like to do this too, then to get this to work go into the Google Home app on your phone, tap the 'Routines' icon, tap the colourful '+' sign in the bottom right of the screen, tap 'Add Starter', tap 'When I say to Google Assistant', enter phase you are working with but do not include the word 'activate' - for example "open the calculator" (without the quotes), tap 'Add starter', tap 'Add Action', tap 'Try adding your own', enter the same phase as above but this time be sure to include the 'activate' at the beginning of it - for example "activate open the calculator" (without the quotes), tap 'Done'.
Upon opening Google Home App, I could not find the 'Routines' icon you mentioned above thus preventing me to proceed with the rest of the steps.
Please advise