Need help potty training rat?

I have a litter box in the corner of his cage, where I use Carefresh ultra. And I use fleece for his bedding.I have him for a month now been training him for 3 weeks or more. He sometimes will go in his box but more often go on his fleece. He also tends to kick the litter out of the litter box and pee and poo goes all over, also making him start to smell (having to wash him more) He also goes underneath the fleece and likes to make a mess and sleep and pee underneath the fleece on the bare surface of the cage. Making the cage stink. Any help please?? Thanks! And no stupid answers:)