Nice cat box. My sister built her cat box into the wall between the kitchen and the garage. The cat enters from the kitchen and does its business in the litter box which is in an enclosure on the garage side of the wall. We've tried a lot of things, first basic plastic litter box, then got one of those electronic auto scooping boxes, now we just have one of the litter boxes with a cover. We were/are not happy with any of the solutions.
The best improvement has been a new type of litter. Though expensive we started using the "Worlds Best Litter" which is available at PetSmart, Tractor Supply, etc. It is made from corn meal or something related instead of clay. It really controls the odor much better and outlasts regular litter by a big margin. It clumps like crazy too. An aroma (not the typical ammonia smell) starts to grow when it is time to change.
The cat still will track some of the litter into the house, especially when it gets closer to needing to be changed and has become a little powdery.
The solution: Potty train the cat!