About putting veggies on the bottom, under the meat:
I do this with potatoes, carrots, peppers and onions. BUT, when I make a pot roast or beef stew, my family loves lots of mushrooms in it. I find that it's better to leave the mushrooms whole, and put them on top of the meat. Also, I cut the liquid even more because mushrooms will contribute liquid to the recipe. It's amazing how much even the "big" mushrooms will shrink after 8 hours in the crock pot!