Rick, start with a 1/4 brick and knead it for a while to get it to soften up. Then roll out to a 2 to 3 MM thickness. The roller is only 4 inches wide and for me 16 long is about as long as I can manage. Keep adding clay until you get the dimensions you want. If rolling in place lay the entire section in place to the desired thickness and trim excess from edges. Then roll the brick in one continuous motion. As Mark found out different substrates absorb water at different rates, which can result in cupping. My next attempt will be to model building bricks in a 1 to 2 MM sheet. When dry the stuff is pretty firm and rigid. Getting it to dry slow enough not to warp will be the challenge. We've posted other tips on working with the clay and roller to get things to release or stay stuck to the substrate.
There are 2 kinds of rolling taking place here. First is to use something to flatten the clay into a smooth uniform surface, The second rolling is using the patterned roller. I used a 1/2 inch diameter steel rod. A wooden rolling pin is another option.
