What are the best ways to Automate JSON POST Request using Restassured API.

My POST request is too big and all my endpoints requests are too bit.
Appreciate your help on this.

For Ex:

{
      "async": false,
      "shipper_accounts": [
        {
          "id": "00000000-0000-0000-0000-000000000000"
        }
      ],
      "is_document": false,
      "shipment": {
        "ship_from": {
          "contact_name": "Elmira Zulauf",
          "company_name": "Kemmer-Gerhold",
          "street1": "662 Flatley Manors",
          "country": "HKG",
          "type": "business"
        },
        "ship_to": {
          "contact_name": "Dr. Moises Corwin",
          "phone": "1-140-225-6410",
          "email": "[email protected]",
          "street1": "28292 Daugherty Orchard",
          "city": "Beverly Hills",
          "postal_code": "90209",
          "state": "CA",
          "country": "USA",
          "type": "residential"
        },
        "parcels": [
          {
            "description": "Food XS",
            "box_type": "custom",
            "weight": {
              "value": 2,
              "unit": "kg"
            },
            "dimension": {
              "width": 20,
              "height": 40,
              "depth": 40,
              "unit": "cm"
            },
            "items": [
              {
                "description": "Food Bar",
                "origin_country": "USA",
                "quantity": 2,
                "price": {
                  "amount": 3,
                  "currency": "USD"
                },
                "weight": {
                  "value": 0.6,
                  "unit": "kg"
                },
                "sku": "imac2014"
              }
            ]
          }
        ]
      }
    }