Coat chicken with salt, cayenne pepper, paprika, curry powder, and ginger. Add peach preserves, vinegar, and soy sauce to gallon freezer bag. Add in sweet potatoes and onion, and top with chicken. Seal bag and place in freezer. When ready to use thaw in fridge overnight. Empty the contents out of the bag and into crock pot. Cover and cook on low for 6-8 hours until chicken is thoroughly cooked and sweet potatoes are tender when pierced with fork.
Combine chicken broth and cornstarch and mix well. Add to slow cooker. Cover and cook on high 10-15 minutes until sauce is thickened.