SharePoint and Power Automate manually bulk list items

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What is the good hyperlink syntax to start a flow with SharePoint button webpart?

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Goal : Click one button (outside SPO list) and start a Power Automate flow

Context on SharePoint :

1. Create SPO List named : "DemoList" .
2. Create SPO site page, add button webpart and add "DemoList" with list webpart on the page.
3. Someone will enter like 50 new items by month in "DemoList"
4. When they need someone to approve new items, this person will click on the button. (When they click, the flow will notify Finance and send by user an email with decision details. 
5. Flow will use a System Account

If SPO Button webpart click, start Power Automates flow.

I know that we can add Approval button in a column, but I think the end user don't want to click 50 items by month when user need it.