Hi, Freceena,
I do not think you can use a URL to make the list new form fields pre-filled with your required values. As you mentioned flow, I will assume you are using SharePoint Online, please let me know if that is not your scenario.
Using flow you can create items and set the list item field with values you need. Then you can send an email to users with a link of the newly created item. Then end user will be able to directly edit the item. The tiny difference will be that end user will
need to click edit item.
A simple demo here, set the trigger as you wish.

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Jerry
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