Mix the flour, yeast, salt and sugar. Sift them in a large bowl. Cut the spinach at in small pieces and soak for at least some water, melt the margarine, beat egg and add it to the flour. Top up and 300 ml water. Knead the dough for about 10 minutes and then leave to rise in a warm place. It must increase its volume twice. When risen disc it roll square (40x40 cm) and sprinkle with crumbled feta cheese. Wrap the dough into a roll and place it in the tray. With a sharp knife make incisions on its surface. Bake in preheated oven at 180-200 C for 50-60 minutes.