If you want to use a foreground service, then the only possibility is to get familiar with the itoo extension Open Source • Background Tasks: Itoo 🚀
However there are 2 main disadvantages for your use case
Usually you do not want a persistent notification being displayed for the user while your background process is running, which is required for itoo
Also usually you want to keep battery usage of your device as low as possible... a process running in the background to compare regularly if it is already time to send a notification drains your battery...
That's why usually you would use the alarmmanager functionality of the Android operating system to get triggered at the given time. My paid alarmmanager extension would be able to help...
Taifun