Keep pierogi in your freezer for quick family dinners: You can add them to soup or use in place of ravioli.
For enhanced depth of flavor, consider briefly searing the chicken thighs in a pan before adding them to the slow cooker; this develops a rich fond. When whisking the flour and broth, ensure it's completely smooth to prevent lumps in the final sauce. The use of frozen pierogi makes this dish convenient; for a more traditional approach, homemade drop biscuits or simple flour dumplings can be added during the last hour of slow cooking. Adjust seasoning with salt and pepper at the end, as slow cooking can sometimes mellow flavors. Fresh dill is excellent, but a mix of parsley and chives would also complement the dish beautifully.