Set default layout to stacking (I prefer stack/stack or master-stack).

i3/config.simple

@@ -28,6 +28,9 @@ client.unfocused        $bgucolor $bgucolor $txtucolor $indcolor $bgucolor
 #client.placeholder      #000000 #0c0c0c $txtacolor #000000
 #client.background       #2B2C2B
 
+# set default desktop layout (default is tiling) <default|stacking|tabbed>
+workspace_layout stacking
+
 # Configure border style <normal|1pixel|pixel xx|none|pixel>
 for_window [class=".*"] $border_no_name