В CMainFrame::OnCreateClient
// Create splitter with 2 rows and 1 col
m_wndSplitter.CreateStatic(this, 2, 1);
// Create a view in the top row
m_wndSplitter.CreateView(0, 0, RUNTIME_CLASS(CView1), CSize(100, 100), pContext);
// Create a 2 column splitter that will go in the bottom row of the first
m_wndSplitter2.CreateStatic(&m_wndSplitter, 1, 2, WS_CHILD|WS_VISIBLE, m_wndSplitter.IdFromRowCol(1, 0));
// Create views for the bottom splitter
m_wndSplitter2.CreateView(0, 0, RUNTIME_CLASS(CView2), CSize(100, 100), pContext);
m_wndSplitter2.CreateView(0, 1, RUNTIME_CLASS(CView3), CSize(100, 100), pContext);
...