Using a small serrated knife, carefully split pitas into top and bottom halves. Spread about ⅓ cup of homemade falafel into a thin layer over each pita half.
Heat 2 teaspoons of the olive oil in a large skillet over medium. Working with 1 pita half at a time, place pita falafel-side-down into skillet and press firmly with a flat spatula. Cook, undisturbed, until falafel is golden brown and edges are crisped, 3 to 4 minutes. Transfer to plate, falafel-side-up. Repeat with remaining oil and pita, adding 1 teaspoon oil to skillet in between each pita.
Top falafel with shredded lettuce, chopped tomatoes, chopped cucumber, and pickles. Drizzle with tahini sauce and zhug, if desired. Fold pitas in half over fillings and serve warm.
