Make the pita bread: In a container, whisk together the lukewarm water, instant yeast, and granulated sugar until dissolved. In a large bowl, mix the bread flour and fine sea salt. Pour the yeast mixture into the flour mixture and stir by hand to form a shaggy dough. Knead for 3-4 minutes until smooth. Cover and let rise for 1 hour at room temperature or overnight in the fridge.

Preheat the oven with an inverted baking sheet or baking steel inside to 475°F (246°C) for 30 minutes. Punch down the dough and divide into 8 pieces (about 150 g each). Form each piece into a ball, cover, and let rest for 15 minutes. Roll each ball into a 7-8 inch disc and bake one at a time on the hot baking surface for 1-2 minutes per side.

Make the pork souvlaki: Cut the pork into ½-inch slices and combine with the oregano, paprika, black pepper, kosher salt, rosemary, garlic, and vegetable oil. Mix well to form a paste. Thread the seasoned pork onto long skewers, stacking the slices. Roast the skewers on a foil-lined baking sheet with a wire rack at 400°F (204°C) for 45 minutes, rotating often, until cooked to 155-160°F (68-71°C) internal temperature.

Make the tzatziki: In a medium bowl, combine the Greek yogurt, grated and lightly salted cucumber, parsley, grated garlic, and olive oil. Season with salt and pepper.

Assemble the souvlaki: Place the freshly sliced pork on the pita bread, top with tzatziki, thinly sliced red onion, sliced tomatoes, and crispy french fries. Garnish with fresh parsley if desired.