Freeze toolbar at top of screen

Using a toolbar type main layout with views added into a childwrapper the whole screen can scroll and the toolbar disappears out the top.

Many of the Vaadin addons demos do the same.

Using flex as per the Vaadin docs and training videos do not seem to handle this.

What needs to be done so the toolbar is frozen and the under contents can be scrolled?

AppLayout at least has this type of structure out of the box.