PUT /_ilm/policy/my-ilm-test-policy
{
  "policy" : {
    "phases" : {
      "hot" : {
        "actions" : {
          "rollover" : {
            "max_size" : "50gb",
            "max_age" : "30d"
          },
          "set_priority" : {
            "priority" : 100
          }
        }
      },
      "delete" : {
        "min_age" : "100d",
        "actions" : {
          "delete" : {
            "delete_searchable_snapshot" : true
          }
        }
      }
    }
  }
}

PUT /_index_template/my-ilm-test-template
{
  "index_patterns" : ["my-ilm-test-idx-*"],
  "priority" : 1,
  "template": {
    "settings" : {
      "index.lifecycle.name": "my-ilm-test-policy",
      "index.lifecycle.rollover_alias": "my-ilm-test-index",
      "index.number_of_replicas" : 2
    }
  }
}

PUT my-ilm-test-idx-000001
{
  "aliases": {
    "my-ilm-test-index": {
      "is_write_index": true 
    }
  },
  "settings" : {
    "index" : {
      "number_of_shards" : "1",
      "number_of_replicas" : "2"
    }
  }
}