Place one packet of frozen filo in fridge (from freezer) overnight to defrost (if you forget, it also works to take from freezer and leave on counter a few hours, I've done both).
Preheat oven to 375.
Chop the herbs, halve the tomatoes, quarter and thinly slice the eggplant, slice the scallions and slice asparagus on an angle into 1" ish slices, as per photo.
Measure out 1/4 cup olive oil. This is all you will use for making the pizza.
For good measure, either spray sheet pan lightly with spray oil or brush a teaspoon of oil on pan, just to be sure the filo doesn't stick. Don't overdo it.
Open the defrosted filo dough, unroll it (you will be unrolling multiple layers), and place a damp cloth over all of the layers.
Lay your first layer of dough down. Ultimately you will lay a total of 6 layers of the dough sheets, using it all up and spreading oil on each layer, before you lay the next. How you decide to lay the initial layer (and subsequent layers) will depend on the pan/dough size. For example, my dough sheets were pretty small (about 8"x 13") and my sheet pan was large (13" x 18"), so I laid three sheets across the 18" length of the pan, overlapping them 1-2"(see photo).
Begin the layering process. In between each layer, you will drizzle a spoonful of oil over the dough gingerly. In an effort to keep this pizza light and avoid greasiness, please take care with this process. Drizzling and using the spoon to try and spread it a bit works. It is not necessary to cover the entire surface with the oil.
Now that the dough is all layered onto the pan, you can begin to layer the ingredients over the dough. Leave about 1" of the dough uncovered, around the edges and fold that 1" in, with a couple small rolls/folds - see photo.
Lay the herbs and crumble the feta, then artfully scatter the rest of the veggies, finishing with halving and scattering the Ciliegine mozzarella balls.
The final touch before baking the pizza is to sprinkle any left over oil (or drizzle a tad extra) across the pizza and sprinkle with dried oregano and pepper flakes (if you like a bit of spice).
Bake for 30 minutes, checking after 20 minutes and aiming for a golden but not dark brown crust. Slice into 8 pieces and enjoy. Reheat in oven (filo won't reheat will in a microwave).