From covering it, absorbing it, to eliminating it - you'll need a mix of all three methods to keep a litter box from smelling. I've managed to figure it out with 5 foster kittens living in a tiny New York City apartment.

As seen in video:
Sifting Litter Box (Arm and Hammer): https://amzn.to/3OLwHNV
Pine Litter (World's Best): https://amzn.to/3SjSeTb
Corn Litter (Feline Pine): https://amzn.to/3TVZfKT
Litter Scooper (WePet): https://amzn.to/3HlnqLr
Litter Mat (Amazon Basics): https://amzn.to/3Sh5XKc
Top Entry Litter Box (IRIS): https://amzn.to/3Hj98e8
Step Trash Can (mDesign): https://amzn.to/3RTLHNz

Please consider fostering for a shelter or rescue near you.