Uploading Files to OpenAI /files endpoint

Has anyone successfully uploaded a file using the Retool OpenAI resource to the POST /file endpoint?

I've tried many different formats and keep getting back:

  "error": {
    "message": "The browser (or proxy) sent a request that this server could not understand.",
    "type": "server_error",
    "param": null,
    "code": null

I've been trying to populate the file field in the request with a value from a file upload component. That component seems to turn anything into Base64, so maybe OpenAI is rejecting this?

Here's what I'm seeing:

It seems like OpenAI just wants the CSV and not the base64 conversion, but is there a way to just send the actual CSV file from the filepicker?