var leftColumn = new ColumnBlockRequest()
{
	Column = new ColumnBlockRequest.Info()
	{
		Children = new[]
		{
			new HeadingOneBlockRequest()
			{
				Heading_1 = new HeadingOneBlockRequest.Info()
				{
					RichText = new List<RichTextBase>()
					{
						new RichTextTextInput()
						{
							Text = new Text() { Content = "Left" }
						}
					}
				}
			}
		}
	}
};
var rightColumn = new ColumnBlockRequest()
{
	Column = new ColumnBlockRequest.Info()
	{
		Children = new[]
		{
			new HeadingOneBlockRequest()
			{
				Heading_1 = new HeadingOneBlockRequest.Info()
				{
					RichText = new List<RichTextBase>()
					{
						new RichTextTextInput()
						{
							Text = new Text() { Content = "Right" }
						}
					}
				}
			}
		}
	}
};
var request = new BlockAppendChildrenRequest()
{
	BlockId = _page.Id,
	Children = new List<IBlockObjectRequest>()
	{
		new ColumnListBlockRequest()
		{
			ColumnList = new ColumnListBlockRequest.Info()
			{
				Children = new List<ColumnBlockRequest>()
				{
					leftColumn,
					rightColumn
				}
			}
		}
	}
};
await Client.Blocks.AppendChildrenAsync(request);