Welcome back! Do you know how to make a wrap around gusset? if you haven’t done one yet then you should. You should also go back through the lesson you have finished and refresh yourself, you don’t have to redo them just refresh.
If you want the flap to bend in certain places yes you should use a stay. Remember a stay doesn’t have to be made from Bontex. It depends on how stiff you want it to be that will determine what you make the stay out of.
Good to see you again!