I have a new 20 qt. programmable roaster oven, and for some reason I misplaced the manual on it. Can someone tell me if I can use this as a slow cooker and if so am I supposed to take all the trays out and only use the one that does not come out, because right now I am useing it as we speak, but I have all but one big removable pan still in it, and I put a tad bit of water under that pan and am trying to cook in it that way, but to me it seems wrong, please someone help me. thank you Pat Crawford