object/run/1 matches the site

public static HumanMadeObject RUN_1_Multiple_Artists()
{
    var run = new HumanMadeObject()
        .WithContext()
        .WithId("https://linked.art/example/object/run/1")
        .WithLabel("RUN")
        .WithClassifiedAs(Aat.Painting, Aat.TypeOfWork);

    run.ProducedBy = new Production()
    {
        Part = [
            new Production()
            {
                Technique = [Aat.Term("300054216", "Painting")],
                CarriedOutBy = [
                    new Person()
                        .WithId("https://linked.art/example/person/barrow")
                        .WithLabel("Mark Barrow")
                ]
            },
            new Production()
            {
                Technique = [Aat.Term("300053643", "hand weaving")],
                CarriedOutBy = [
                    new Person()
                        .WithId("https://linked.art/example/person/parke")
                        .WithLabel("Sarah Parke")
                ]
            }
        ]
    };

    return run;
}

• Metatype classification The second argument classifies the first, not the object: WithClassifiedAs(Aat.Description, Aat.Statement) says this is a Description, and Description is a kind of Statement. The Plain C# form shows the nesting.
• Terms outside the registry The vocabulary registry holds only the terms linked.art itself publishes, so a dataset's own concepts, places and people are written with Aat.Term, Tgn.Place and Ulan.Person, giving the id and the label.

var humanMadeObject = new HumanMadeObject
{
    Context = ["https://linked.art/ns/v1/linked-art.json"],
    Id = "https://linked.art/example/object/run/1",
    Label = "RUN",
    ProducedBy = new Production
    {
        Part =
        [
            new Production
            {
                CarriedOutBy =
                [
                    new Person
                    {
                        Id = "https://linked.art/example/person/barrow",
                        Label = "Mark Barrow",
                    },
                ],
                Technique = [Aat.Term("300054216", "Painting")],
            },
            new Production
            {
                CarriedOutBy =
                [
                    new Person
                    {
                        Id = "https://linked.art/example/person/parke",
                        Label = "Sarah Parke",
                    },
                ],
                Technique = [Aat.Term("300053643", "hand weaving")],
            },
        ],
    },
    ClassifiedAs =
    [
        new Type("http://vocab.getty.edu/aat/300033618", "Painting")
        {
            ClassifiedAs = [Aat.TypeOfWork],
        },
    ],
};

Generated from the object the example builds: every property that is set, as object initialisers, with the vocabulary constants where a term is in the registry. The fluent helpers are a convenience, not a requirement; this form and the one as written produce the same JSON.