OPTIONAL: In a large skillet over medium heat, toss the lamb cubes with 2 tablespoons of olive oil. Cook for 3 minutes, until the outside of the lamb is browned. Drain any excessive fat and oil.
Add the lamb cubes to the slow cooker. Sprinkle with dried rosemary, dried thyme, allspice, salt and pepper. Pour in the broth and stir. Push the lamb to one side of the slow cooker and add the sliced garlic cloves on top. To the other side, add the potatoes and carrots.
Cover and set to HIGH for 4 hours or LOW for 8 hours. *See notes for cook time tips.
Transfer to a serving dish when finished, reserving extra broth for serving.
Notes
Cook Time and Temperature: My preference is to slow cook lamb stew on LOW. This is also my preference when slow cooking any meat in the crock pot. The meat has more time to tenderize when cooked for a longer time and at a lower temperature. But there is nothing wrong with using the HIGH setting, especially if you don't have a lot of time.