So, my boys have this thing they like to do where they dig all the way to the bottom to do their business. So everything sticks to the bottom of the box and I have to pry it up with the litter box scoop. Any suggestions for preventing the clumps from sticking to the bottom? I clean the boxes (we have 2) at least twice a day which means the clumps are still kinda wet and that makes it even harder to pry them up.