tldraw/apps/docs/app/not-found.tsx

import { Header } from '@/components/Header'
import { Sidebar } from '@/components/Sidebar'
import { getDb } from '@/utils/ContentDatabase'

export default async function NotFound() {
	const db = await getDb()
	const sidebar = await db.getSidebarContentList({})

	return (
		<div className="wrapper">
			<div className="layout">
				<Header />
				<Sidebar {...sidebar} />
				<main className="main-content article">
					<div className="page-header">
						<h1>Not found.</h1>
					</div>
					<p>There's nothing here. :(</p>
				</main>
			</div>
		</div>
	)
}