The ICraftingInventory contains all kinds of information on the inventory a crafting process is performed in.

It might be required to import the class to avoid errors.
import crafttweaker.recipes.ICraftingInventory

ZenGetter	Return type	Description
ZenGetter player	Return type IPlayer	Description the player owning this inventory
ZenGetter size	Return type int	Description the inventory's size
ZenGetter width	Return type int	Description the inventory's width
ZenGetter height	Return type int	Description the inventory's height
ZenGetter stackCount	Return type int	Description the the number of stacks that are actually filled in
ZenGetter items	Return type IItemStack[][]	Description The items that present in the crafting table
ZenGetter itemArray	Return type IItemStack[]	Description The items that present in the crafting table

Following Methods are available:

inventory.getStack(index) returns the IItemStack at the given index or null if no item present. Index is an int.
inventory.setStack(index, item) sets the Stack at the given index to the provided item. Index is an int, item is an IItemStack. Use null if you want to clear the stack at that index.

The top left stack is position (0, 0), row and column are ints.
inventory.getStack(row, column) returns the IItemStack at the given position or null if no item present.
inventory.setStack(row, column, item) sets the stack at the given position to the provided item. Item is an IItemStack. Use null if you want to clear the stack at that position.