In a large saucepan, add 1 tsp olive oil and sauté the garlic (thinly sliced) and crushed red pepper for ~1-2 minutes on medium high.
Once lightly toasted and fragrant, add your spinach, a handful at a time, and cover until wilted. Do this with all of your spinach. (don’t worry it will cook down)
Once all of your spinach is wilted, drain through a colander, ensuring you get a majority of the accumulated liquid out. Toss with feta cheese and set aside in fridge to cool for at least 10 minutes.
Brush an 8-10” cast iron pan liberally with olive oil and begin layering your phyllo dough in the pan. Alternate layers’ direction as to ensure even coverage and brush with more olive oil in between each layer. Use half of your dough on the bottom. Then evenly spread the spinach mixture along the bottom half of the dough, leaving a 1/4” gap around the outside. Finish by repeating the process for the top half of phyllo dough, and finally pinching the top and bottom together.
Score the pastry on top using the top of a sharp knife. I used a small cup to ‘trace’ the center out and then scored lines for 8 even slices. You can score this however you prefer.
Make an egg wash by whisking a cracked egg and 1-2 tbs of water. Brush the top of the pastry lightly with egg wash and season with salt. Place in a 350° oven for ~25 minutes or until top is golden brown and crispy.
Once browned remove from oven and allow to cool before slicing through your score marks and serving!