Based on https://www.youtube.com/watch?v=ZQPknck1kmo:

• Open Task Scheduler
• Create Basic Task… (right action bar)
• Action: start a program
• Program/script: C:\Windows\System32\wsl.exe
• Arguments: /home/slack/bin/whatever_backup_script.sh
• Check “open the properties dialogue for this when I click finish” (more scheduling options, etc)