Season the chicken with dried poultry seasoning, salt and pepper. Add to a bag with sliced lemon, chopped garlic, chili pepper, oregano and rosemary. Marinate for several hours or overnight. Bring to room temperature, then cook on a hot grill or grill pan over medium-high heat 12-15 minutes. Let rest, then slice on angle; douse with the juice of 1 lemon.
For the sauce, salt the shredded cucumber and drain in a strainer for 20-30 minutes. Press out all the liquid you can and transfer to a food processor with the yogurt, feta, dill, parsley, salt, pepper, the juice of the remaining halved lemon and the grated or pasted garlic; process until smooth.
Grill the bread.
Slather the grilled bread with sauce; top with the sliced chicken and some diced vegetable salad.