object/okeeffe-gok/1 matches the site

public static HumanMadeObject OKeeffe_Gok_1()
{
    var gok = new HumanMadeObject()
        .WithContext()
        .WithId("https://linked.art/example/object/okeeffe-gok/1")
        .WithLabel("GOK 1918, GOKM")
        .WithClassifiedAs(Aat.Photograph, Aat.TypeOfWork);

    gok.IdentifiedBy = [ new Identifier("2014.3.78").AsAccessionNumber() ];

    gok.Shows = [
        new VisualItem()
            .WithId("https://linked.art/example/visual/okeeffe")
            .WithLabel("Visual Content of GOK 1918")
    ];

    gok.ProducedBy = new Production().WithLabel("Printing of Photograph");
    gok.ProducedBy.UsedSpecificObject = [
        new HumanMadeObject()
            .WithId("https://linked.art/example/object/okeeffe-negative")
            .WithLabel("Negative of GOK 1918")
    ];

    return gok;
}

• 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.
• Role shortcuts AsPrimaryName, AsAccessionNumber and AsSystemAssignedNumber each add a single classification, with the AAT terms Primary Name, Accession Number and System Number.

var humanMadeObject = new HumanMadeObject
{
    Context = ["https://linked.art/ns/v1/linked-art.json"],
    Id = "https://linked.art/example/object/okeeffe-gok/1",
    Label = "GOK 1918, GOKM",
    ProducedBy = new Production
    {
        Label = "Printing of Photograph",
        UsedSpecificObject =
        [
            new HumanMadeObject
            {
                Id = "https://linked.art/example/object/okeeffe-negative",
                Label = "Negative of GOK 1918",
            },
        ],
    },
    Shows =
    [
        new VisualItem
        {
            Id = "https://linked.art/example/visual/okeeffe",
            Label = "Visual Content of GOK 1918",
        },
    ],
    ClassifiedAs =
    [
        new Type("http://vocab.getty.edu/aat/300046300", "Photograph")
        {
            ClassifiedAs = [Aat.TypeOfWork],
        },
    ],
    IdentifiedBy =
    [
        new Identifier("2014.3.78")
        {
            ClassifiedAs = [Aat.AccessionNumber],
        },
    ],
};

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.