object/gradualpage/1 matches the site

public static HumanMadeObject GradualPage_1_PartRemoval()
{
    var gradualPage = new HumanMadeObject()
        .WithContext()
        .WithId("https://linked.art/example/object/gradualpage/1")
        .WithLabel("Page from a Gradual")
        .WithClassifiedAs(Aat.TextOfAPage, Aat.TypeOfWork);

    gradualPage.RemovedBy = [
        new PartRemoval()
        {
            Diminished = new HumanMadeObject()
                .WithId("https://linked.art/example/object/gradual")
                .WithLabel("Gradual")
        }
    ];

    return gradualPage;
}

• 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.

var humanMadeObject = new HumanMadeObject
{
    Context = ["https://linked.art/ns/v1/linked-art.json"],
    Id = "https://linked.art/example/object/gradualpage/1",
    Label = "Page from a Gradual",
    ClassifiedAs =
    [
        new Type("http://vocab.getty.edu/aat/300194222", "Page")
        {
            ClassifiedAs = [Aat.TypeOfWork],
        },
    ],
    RemovedBy =
    [
        new PartRemoval
        {
            Diminished = new HumanMadeObject
            {
                Id = "https://linked.art/example/object/gradual",
                Label = "Gradual",
            },
        },
    ],
};

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.