Start by combining the bread flour, rapid-rise yeast, sugar, salt, mahleb, and mastic in a large bowl or stand mixer bowl.

Next, add the orange zest, eggs, milk, and melted butter. Mix on low speed with the dough hook until a sticky dough forms.

Place the dough in a lightly greased bowl and cover it with a towel. Let it rise in a warm place for about 1 hour, or until doubled in size.

Turn the risen dough onto a lightly floured surface and divide it into 3 equal pieces, covering them with plastic wrap.

Flatten each piece and roll it into a rectangle. Roll each rectangle up like a Swiss roll, seal the seam, and roll into a rope.

Pinch the rope ends together, braid loosely, tuck the ends under, and place the loaf on a lined baking sheet.

Cover it loosely and let it rise for 60 to 90 minutes. Preheat the oven to 350°F at least 30 minutes before baking.

Brush the loaf with the beaten egg, scatter the flaked almonds over the top, and bake for 40 to 45 minutes until deep golden.

Let the loaf cool on a wire rack before slicing.