There are a lot of options on how to place a smart lock, but the probably simplest and most secure is, to choose a place where it is secure to leave your phone unlocked, for example your home adress. As soon as you are in reach of the area you placed your Smart lock in, your device will automatically unlock, when you leave, it will be locked again.

Android 9
Step 1:  Open the  settings
Step 2:  Tap on  Security & location
Step 3:  Tap on  Smart lock
Step 4:  Tap on  Trusted places
Step 5:  Tap on  Add trusted place
Step 6:  Confirm with  Select this location
Step 7:  Confirm with  Select
  1. Open the settings
  2. Tap on Security & location
  3. Tap on Smart lock
  4. Tap on Trusted places
  5. Tap on Add trusted place
  6. Confirm with Select this location
  7. Confirm with Select

Android Instructions
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