Cut one garlic clove in half and rub roast all over with it.
Place roast and whole garlic clove in slow cooker.
Add remaining ingredients (except for sauce) to the slow cooker, sprinkling spices directly on meat.
Cover and cook on high 5-6 hours or low 7-8 hours.
Remove meat from crock and shred with a fork.
Return meat to the crock and stir to combine with juices from cooking the meat.
Stir yogurt, cucumber and mint together.
Serve meat in pita bread with yogurt sauce.