When you order hair with a curl, a lot of the curl tends to be at the ends of the hair and either drops out or gets cut out if you wear the hair shorter.

A good idea is to ask for the curling rods to be used right at the base of the hair which will help give it the lift & volume for the style you want.

I've not ordered flat back before, but I have ordered freestyle with a 'front lift' and this means it ventilated upwards.
I really liked it because it was still versatile but kept its shape well too.

If I were you, I'd consider forward ventilation from the crown and lift at the front.