First, Craft Item now works. The problem may have been with Facebook unavailability, not related to MobWars LCN. Second, the weapon workshop works by combining objects, weapons, transport or armor, to make other objects. In most cases, many makes one. So you loose the multiple value of each object for (hopefully) a higher value object (where value is the offense/defense value).
And you have to for the first item you are crating have to have the needed items and put them in the spots next time you craft that item you can do it automatically bit ya still need certain items to craft usually it consists of a gift and an adventure/ job drop and sometimes a boss drop snd coins