Start by making sure your puff pastry is at room temperature by taking it out of the fridge about 30 minutes before using (if frozen, thaw overnight in the fridge).

Using a lightly floured surface, roll out the puff pastry sheet (if not already rolled), and cut into square shapes about 2" in length/width. You can make them smaller or larger depending on your preference.

Mix the feta, olives, and za'atar together in a bowl. Taste and adjust to your liking.

Create a 1/4 inch think line around the puff pastry squares by pressing down using something sharp (other end of a spoon). Don't actually cut the dough, simply make an indentation. 

Lightly pierce the middle of the puff pastry several times with a fork, ensuring you don't do this to the edges. This makes sure that the middle part doesn't puff up and dislodge the filling

Arrange the squares on a parchment lined baking sheet, and spoon the mixture and spread evenly around the square, leaving the edges empty.

Pop into the oven at 400F for roughly 10-15 minutes, or until the edges are golden brown. Enjoy!