Flatbread With Avocado and Scallion Salsa

Stir sugar into ¾ cup warm water in a large bowl. Sprinkle in yeast and let sit until foamy, about 10 minutes.
Add flour, yogurt, oil, and kosher salt to sugar mixture and mix until a shaggy dough forms (don’t worry about any dry or unincorporated bits). Cover bowl with a damp kitchen towel and let sit in a warm, dry spot until doubled in size, about 1 hour.
While the dough is rising, toast coriander seeds and cumin seeds in a dry medium skillet over medium heat, shaking often, until fragrant and slightly darkened in color, about 3 minutes. Transfer to a spice mill. Let cool, then coarsely grind. Set spice mixture aside.
Place scallions and 1 Tbsp. oil in skillet, season with kosher salt, and cook, turning occasionally, until softened and deeply charred, about 4 minutes. Transfer to a cutting board; trim roots and discard. Finely chop scallions and place in a medium bowl. Add reserved spice mixture, chile, and parsley. Finely grate half of lemon zest into bowl, then cut lemon in half and squeeze in juice. Add 1 cup oil and stir well to combine. Season with kosher salt and let sit while you make the flatbreads.
Turn out dough onto a lightly dusted surface and divide into 8 equal pieces. Form into balls and, working with 1 ball at a time, roll out into 6" rounds about ¼" thick.
Heat 1 Tbsp. oil in a large skillet over medium-high. Working 1 at a time and adding remaining 2 Tbsp. oil as needed, cook flatbread until bubbles appear over the surface, about 1 minute. Flip and cook until cooked through, about 1 minute. Continue to cook, turning often, until browned in spots on both sides, about 1 minute longer. Transfer to a plate and wrap up in a clean kitchen towel to keep warm.
To serve, brush each flatbread with oil. Coarsely smash avocados onto flatbread and spoon salsa over. Sprinkle with sea salt if desired.