Hi @PeterDonohue ,
You could refer to link below to send the collection data from PowerApps to flow:
https://www.powerobjects.com/blog/2019/09/19/send-a-collection-from-powerapps-to-flow/
You could refer to link below to start a flow on PowerApps:
https://docs.microsoft.com/en-us/powerapps/maker/canvas-apps/using-logic-flows
Ans I have made a test on my side to create a collection as below:

Add a button, the Onselect property to run the flow name "PoserAppsbutton"set to:
PowerAppsbutton.Run(JSON(ProductList))
Then you could refer to screenshot below to create the flow:

The schema as below:
{
"type": "array",
"items": {
"type": "object",
"properties": {
"Email": {
"type": "string"
},
"Product": {
"type": "string"
}
},
"required": [
"Email",
"Product"
]
}
}
Best regards,
Alice
Community Support Team _ Alice Zhang
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