From the products (excluding the butter and feta), knead a dough, divide it into 3 balls. Let them rest for about 10 min. Take 1 ball and roll it out to the diameter of the form (11″ (28 cm)).
Place the rolled out sheet into the greased form, smear with just a little bit of butter, sprinkle with feta cheese and proceed with the next sheet the same way.
Once you've placed the 3rd rolled out sheet, cut the whole thing into squares and pour melted butter into the cuts.
Bake at 356°F (180 °C) for about 50-60 min. until ready.
Note: Just to clarify, in some regions of Bulgaria instead of smearing the sheets with butter they smear them with sour cream but personally I don't like it that way because the sheets get too soggy and the loaf turns out a little mushy.
Of course that's just my opinion - you can try making it with sour cream if you like.