Thea meat is there to stop the vegetables not falling off. When you eat them you usually start from the top and keep the meat close to the hand which holds the stick.
You certainly can, although I would agree with @Jeruba that placing the meat on top adds flavor to the veggies below. However if you’re cooking leafy greens in your crock, you might want to keep those on top of everything so they don’t get too soggy.
Solid root vegetables like carrots, turnips, sweet potatoes, etc, would be better on the bottom because they’ll get cooked more thoroughly (the bottom is hotter). Vegetables that need less cooking, like mushrooms and leafy things, would be better on the top.
Having said that when I do crockpot cooking it all gets mixed up together, and doesn’t seem to do any of it any harm, so I don’t think it really matters that much.