Most slow cookers have a hotter side (typically the back side, opposite the side with the controls) that can cause dense casseroles like baked ziti to burn. To solve this problem we lined the slow-cooker insert with an aluminum foil collar. For recipes that we wanted to lift out of the insert intact, we first lined the slow cooker with a foil collar, then lined it completely with foil.

Fold sheets of heavy-duty aluminum foil until you have a six-layered foil rectangle that measures roughly 16 inches long by 4 inches wide. (Depending on the width of the foil, you will need either two or three sheets of foil.) Then press the collar into the back side of the slow-cooker insert; the food will help hold the collar in place during cooking.

Line the slow-cooker insert with a foil collar, then fit two large sheets of heavy-duty foil in the slow cooker, perpendicular to one another, with the extra foil hanging over the edges. Before serving, these overhanging edges can be used as handles to pull the food out of the slow cooker fully intact and transfer it to a platter for serving.

In the moist environment of a slow cooker, there is no opportunity to drive off moisture as there is in an oven, so excess moisture in the form of sauce or liquid that has leached out of vegetables can cause havoc when it comes to casseroles that need cohesiveness. In addition to controlling the amount and thickness of our sauces and fillings, in some cases we also found it important to precook vegetables in order to drive out moisture.

Our casseroles have relatively short cooking times; otherwise, we ended up with mushy pasta, bland vegetables, and dry meat. You’ll find a range of cooking times for casseroles; be sure to follow our guidance on the times and settings for vibrant flavors and properly cooked casseroles.

When making slow-cooker casseroles with pasta, how you handle the pasta makes a huge difference in the success of the dish. For baked ziti, raw or partially cooked pasta did not work, but toasting it with oil in the microwave did, and it prevented the pasta from becoming bloated. We found that microwaving the pasta at 50 percent power, and stirring it occasionally, gently toasted the pasta; note that only a portion will look toasted and blistered.

Many healthy casserole recipes wouldn’t be complete without some cheese to boost flavor. Low-fat options like light cheddar gave our fillings the richness we wanted but became waxy when used as toppings, so we folded the cheese into the filling instead. For a cheesy finish we often chose to use a full-fat cheese (with the exception of mozzarella where part-skim worked fine), or a hard cheese like Parmesan or Asiago, or a soft cheese naturally low in fat like queso fresco or feta.