Which window can I passing a `WM_SYSCOMMAND` to carry out system commands?

An application can carry out any system command at any time by passing a WM_SYSCOMMAND message to DefWindowProc.

If I don't have any windows, which window can I post/send WM_SYSCOMMAND to carry out system commands?

First, GetDesktopWindow() doesn't work.
Second, while GetForegroundWindow() works most of the time, it won't work if the foreground window decides to intercept WM_SYSCOMMAND or has a higher integrity level.
And HWND_BROADCAST is the worst option.

So what about GetShellWindow()?

Or, can I direct call DefWindowProcW(RANDOM_WINDOW, WM_SYSCOMMAND, ...)? It seems that this will work as long as RANDOM_WINDOW is any valid HWND, and the integrity level is no higher than caller.

_{( I'm raising this question because there are some terrible answers about turning off the monitor, such as SendMessage(HWND_BROADCAST, WM_SYSCOMMAND, SC_MONITORPOWER, 2). While some have warned against this in the comments, and Raymond Chen has even written an article about it, even Raymond Chen's solution involves creating a custom window. To fix(edit) these terrible answers, I want to provide an equally simple alternative solution. Because I can't just say "use any your own HWND, if you don't have any window, then create one". For those who unfamiliar with Win32, they won't want to create a custom window specifically for this, and they're unaware of the flaws in these solutions. )}

Edit: It seems everyone thinks I don't know how to create a window or correctly turn off the monitor.

void TurnOffMonitor() {
    auto TurnOffMonitorWndproc = [](HWND hWnd, UINT  uMsg, WPARAM wParam, LPARAM lParam) ->LRESULT {
        if (uMsg == WM_NCCREATE) {
            DefWindowProcW(hWnd, WM_SYSCOMMAND, SC_MONITORPOWER, 2);
            return FALSE;
        }
        return DefWindowProcW(hWnd, uMsg, wParam, lParam);
        };
    WNDCLASSW wc{};
    wc.lpfnWndProc = TurnOffMonitorWndproc;
    wc.lpszClassName = L"TOMWC";
    ATOM classATOM = RegisterClassW(&wc);
    CreateWindowExW(0, MAKEINTATOM(classATOM), L"", 0, 0, 0, 0, 0, HWND_MESSAGE, 0, 0, 0);
    UnregisterClassW(MAKEINTATOM(classATOM), 0);
}

Although I must admit, I don't know how to do this in a language other than C/C++.