text/koot_nightwatch_ch1/2 matches the site

public static LinguisticObject Page_Count()
{
    var chapter = new LinguisticObject()
        .WithContext()
        .WithId("https://linked.art/example/text/koot_nightwatch_ch1/2")
        .WithLabel("Chapter 1 of Koot")
        .WithClassifiedAs(Aat.Chapter, Aat.TypeOfWork);

    chapter.IdentifiedBy = [new Name("Introduction").AsPrimaryName()];

    chapter.ReferredToBy = [
        new LinguisticObject()
            .WithContent("5 - 15")
            .WithClassifiedAs(Aat.PaginationStatement, Aat.Statement)
    ];

    chapter.WithPageCount(10, "10 pages");

    return chapter;
}

• 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.
• Dimensions and physical description Each helper builds a Dimension with its AAT type, value and unit, or a classification with its metatype: height, width, colour, shape, page count, component count, file size, duration in days.

var linguisticObject = new LinguisticObject
{
    Context = ["https://linked.art/ns/v1/linked-art.json"],
    Id = "https://linked.art/example/text/koot_nightwatch_ch1/2",
    Label = "Chapter 1 of Koot",
    Dimension =
    [
        new Dimension
        {
            Label = "10 pages",
            Value = 10,
            Unit = Aat.Pages,
            ClassifiedAs = [Aat.Term("300404433", "Count Of")],
        },
    ],
    ClassifiedAs =
    [
        new Type("http://vocab.getty.edu/aat/300311699", "Chapter")
        {
            ClassifiedAs = [Aat.TypeOfWork],
        },
    ],
    IdentifiedBy =
    [
        new Name("Introduction")
        {
            ClassifiedAs = [Aat.PrimaryName],
        },
    ],
    ReferredToBy =
    [
        new LinguisticObject
        {
            Content = "5 - 15",
            ClassifiedAs =
            [
                new Type("http://vocab.getty.edu/aat/300435440", "Pagination 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.