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