By using endDrawer: ...
instead or in addition to drawer: ...
to set a drawer, like this:
Scaffold(
endDrawer: Drawer(...),
// ...
)
To open it programmatically, use
Scaffold.of(context).openEndDrawer(); //This might have been updated by flutter team since the last edit
See also https://docs.flutter.io/flutter/material/Scaffold/endDrawer.html