AWS endpoint - Authenticate

Hi Need help in creating a authentication header when using AWS endpoints directly instead of AWS boto3 SDK. Using the same access ID and KEY, boto3 code is working, we have to use AWS endpoint directly for some specific reason. This is just a example, ignore content-type and accept. data=data is data what we are passing, that is formatted correctly. Any help will be appreciated. Error message - {'message': 'Missing Authentication Token'}

headers = {
        "aws_access_key_id" : "---------------------------",           
        "aws_secret_access_key" : "----------------------"
        "Content-Type" : "application/x-www-form-urlencoded",
        "Accept" : "application/json"
    }
response = requests.post("https://appflow.us-east-2.amazonaws.com/update-flow", data=data, headers=headers, verify=True)
print(response.json())