I just tossed everything into the crockpot - did not bother simmering the tomatoes, broth and garlic. Because it was a little watery, I decided to add a cup of rice an hour before it was finished, and that made it nice and thick.
I also bought bone-in lamb accidentally, so I ended up with about a pound of lamb, and I think that was good as lamb is pretty flavorful. I think more would have made it over powering.
Definitely will make again. I was careful to cook on low for only 6 hours. I hate overcooked crockpot food.