Power Automatize: pass Powershell JSON parameters to Flow enabled

Background: I have a PowerShell code used to create team sites based on a list column trigger. This works fine

I am also implementing a site design / script that includes a flow trigger.

I have been able to activate my flow but now I want to pass a parameter which is fetched from PowerShell and pass it to the flow. In this case, the parameter is a list item (email) value that I want to use in the flow to send an email to the user when the group site is created and the site layout / script is applied.

The PS json allocation code looks like the following. I added a parameter (testparm) in the json schema presumably to pass it to the Flow JSON code. It didn't work and I thought it didn't, but I tried it anyway. I hope to be near.

$MySiteScript = '
     "$schema": "schema.json",
         "actions": (
          "verb": "triggerFlow",
          "url": "https://prod-103.westus.logic.azure.com:443/workflows/e81c605fcfc64a24a82e6e697cb19750/triggers/manual/paths/invoke?api-version=2016-06-01&sp=%2Ftriggers%2Fmanual%2Frun&sv=1.0&sig=S3Kf8TtbbWzoP6TDuUIKH6CwY5L_TV_HyRtbgdZVMyI",
          "name": "Record and tweet site creation event",
          "parameters": {
            "event": "Microsoft Event",
            "product": "SharePoint",
            "TestParm": "MyTestParm",

             "bindata": { },
     "version": 1

The Power Automate (FLOW) component looks like this.

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