In a large bowl, combine the flour and Greek yogurt. Mix with your hands, then knead for 5 minutes until the dough is soft and elastic. Add more flour if the dough is too sticky. Cover with plastic wrap and set aside while you prepare the filling.
Place all the filling ingredients in a bowl: crumbled feta, cream cheese, finely chopped spinach, minced mint leaves, and minced garlic. Mix well.
Once the dough has rested, knead it again for 30 seconds and then divide it into 4 equal pieces.
Take one dough ball and flatten it slightly with your fingers until it is about 0.8 inches thick. Place a heaping tablespoon of filling in the center, then bring all the corners of the dough to the center around the feta mixture and seal the package.
Turn the package seam side down and flatten the dough with your fingers until the flatbread is about 0.8 inches thick. Set aside and repeat for the remaining flatbreads.
Place a non-stick pan over medium heat without any oil or fat.
Gently place your flatbreads in the pan and cook for 3 to 5 minutes on each side. Flip them when they turn golden brown.
Enjoy with a yogurt sauce or good olive oil with fresh herbs.