WendiQ ... like you, mine usually is a mix of whatever-is-in-the-vicinity at the time and whatever-mood-I-am-in!
The hardest part is finding the bowl that will fit in the crock, and big enough to support the loaf yet shallow enough to fit the height restrictions of the crock and the meatloaf thickness! Once you have that figured out, then you know for the next time. One crock I use upside down custard cups to hold up an upside down plate. Mine are usually one pound of ground plus the add-ins, cooked on high, for about 2 or 3 hours. Your time will vary with the larger amount and dependent on the power and insulation of your crock. First time you make it, don't have a set dinner time, just know you can eat once it's ready. After that you have your time guide to use.
Ladies ... I also do the same suspension method when cooking a chicken in the crock. Makes it much like the roast chickens you get at the grocery deli counters. So moist, and delicious!