For inventory per slab you open your Material Pricebook application. To add a new slab just click the “add product” button at the top of your screen. There will be 7 fields that you need to fill in so your new slab has all the relevant information attached to it. Once you fill in this “new product” selection just click apply. After clicking apply it  will take you to your slab information. Here there will be more options and fields that you can fill in. Fill in as many as are needed.