object/yul_10801219/1 matches the site

public static HumanMadeObject HumanMadeObject_Carries_Linguistic()
{
    var kootCopy = new HumanMadeObject()
        .WithContext()
        .WithId("https://linked.art/example/object/yul_10801219/1")
        .WithLabel("Yale's copy of Koot's Night Watch")
        .WithClassifiedAs(Aat.Book, Aat.TypeOfWork);

    kootCopy.IdentifiedBy = [ 
        new Name("Rembrandt's Night Watch. A Fascinating Story").AsPrimaryName(),
        new Identifier("mfhd:10801219").AsSystemAssignedNumber()
    ];

    kootCopy.ReferredToBy = [
        new LinguisticObject()
            .WithContent("92 p. with illus.")
            .WithClassifiedAs(Aat.PhysicalStatement, Aat.Statement)
    ];

    kootCopy.Carries = [
        new LinguisticObject()
            .WithId("https://linked.art/example/text/koot_nightwatch")
            .WithLabel("Content of Koot's Night Watch")
    ];

    return kootCopy;
}

• 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/yul_10801219/1",
    Label = "Yale's copy of Koot's Night Watch",
    Carries =
    [
        new LinguisticObject
        {
            Id = "https://linked.art/example/text/koot_nightwatch",
            Label = "Content of Koot's Night Watch",
        },
    ],
    ClassifiedAs =
    [
        new Type("http://vocab.getty.edu/aat/300028051", "Book")
        {
            ClassifiedAs = [Aat.TypeOfWork],
        },
    ],
    IdentifiedBy =
    [
        new Name("Rembrandt's Night Watch. A Fascinating Story")
        {
            ClassifiedAs = [Aat.PrimaryName],
        },
        new Identifier("mfhd:10801219")
        {
            ClassifiedAs = [Aat.SystemNumber],
        },
    ],
    ReferredToBy =
    [
        new LinguisticObject
        {
            Content = "92 p. with illus.",
            ClassifiedAs =
            [
                new Type("http://vocab.getty.edu/aat/300435452", "Physical Statement")
                {
                    ClassifiedAs = [Aat.Statement],
                },
            ],
        },
    ],
};

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.