If you know your surfaces are clean, or that you've not operated on a contam surface and the flaps have been stowed the whole time when exposed to contam then de-icing and then anti-icing with flaps up/retracted is logical - the "hidden" parts of the system are clean, and by doing it flaps up you get a longer holdover time.
If you however suspect contam on the parts of the flaps which would be "hidden" when retracted then deploying the flaps to de-ice is pretty much a given, it's the only way to clean the flap leading edges etc. You may then anti-ice in that config (but you'll take a penalty on HOT) or retract first to anti-ice. If you're doing one-step combined anti-ice and de-ice of course, the flaps will have to be down.
NB generic comments, not Airbus-specific.