How to do multipart upload using presigned_post_url (boto3) through HTTP Client

Question

JsonArJson = @"{
    "PresignedURL": {
        "url": "https://random-bucket.s3.amazonaws.com/",
        "fields": {
            "x-amz-server-side-encryption": "aws:kms",

            }
    }
}"
foreach (var field in fields)
{
    formData.Add(new StringContent(field.Value), field.Key);
}
var response = client.PostAsync(JsonArJson.PresignedURL.url.Value, formData).Result;

In the above able to achieve file upload for single put of 5GB. How can we do multipart upload unlike Initiate, parts upload and complete is there any other simple way in .net 6 framewor