Add chicken, Greek Seasoning, 2 Tbsp of olive oil, and a splash of water (chicken stock works too) to your slow cooker. Set to "high" heat for at least 3 hours, or on "low" heat for at least 7 hours. You can always leave it in longer.
Meanwhile, make the tzatziki sauce. In a small bowl, combine the greek yogurt, the juice of half a lemon, 1 Tbsp. of olive oil, half of the diced cucumber, minced garlic, minced dill, and a pinch of salt and pepper. Stir and refrigerate until ready to serve.
When the chicken is done cooking, shred the meat with two forks and stir in the juice of half a lemon.
Using a hot skillet or a gas stove burner, warm the pita bread on both sides, getting some char marks here and there.
To build tacos, spread hummus and tzatziki on the base of the pita bread, and top with shredded chicken, more cucumbers, tomatoes, onions, olives, feta, and fresh mint.
Recipe by Ally's Cooking at https://allyscooking.com/2019/06/05/slow-cooker-greek-chicken-tacos/