you have established a litter type that your cat likes, you can make sure you choose the best box type too. give your cat options. choose easy to clean litter boxes, some covered and some not. some should have low sides and some high sides and some should be large and others small (but all large enough for your cat to easily turn around in).
cleaning and cleaner type: clean boxes by scooping at least once daily and empty completely and clean boxes each week. use a mild soap and rinse thoroughly. if the boxes still smell after cleaning, replace them.
you are encouraging your cat to make a choice that you 