Couscous
When it comes to slow cookers, quick-cooking foods are never a good idea.
Like rice and pasta, this grain will absorb way too much liquid and end up turning into a pile of mush if you try slow cooking it. This stuff is super easy and quick to make on the stovetop.
Lean Meats
Moisture is best for slow cookers.
The problem with lean meats is that they lack the fat content needed to keep the muscle fibers juicy. Dark meats with skin are better for this style of cooking. Or, at minimum, make sure it’s at least a mix of lean vs. fatty.