First off i didnt find this, my friend told me about it.

You cant do it if your host

So first you make sure all boards (except for the bottom one) are down then jump on the bottom board and wait for a zombie to get where its about 5 seconds from getting to the board. Once theres one a little away press start and go to options and change your sensitivty to whatever but make sure you dont keep it the same, then quickly press O (or whatever back back is for xbox) then triangle,this will lag you for about 10 seconds and you might think you frose but its not.... Also you have to do this all before the zombie tears the board down