Open Google Calendar

https://calendar.google.com/

1) Locate your calendar > Click settings and sharing

2) Make this selected calendar available to public

Only do this if you want to!

3) Scroll down to Integrate calendar and copy "Public URL to this calendar" URL

4) Paste it in Notion using "/" (backslash) character and typing "/embed"

5) Select Embed in step 5 and paste it in Notion and select Embed link