The wax form is either carved manually with hand tools and hot knives, or machined either with CNC or manual machine operations. An alternative if you have a completed model to work from is to coat the item with a rubber or silicone compound and carefully cut it from the model after it has hardened. It can then be used to pour liquid wax into to form the wax model. Generally the first method is used to cast the prototype and the resultant casting becomes the model from which the wax mold is produced for production. The wax mold is used to replicated the part in wax multiples for producing the tree of wax forms that ultimately are invested and cast to produce the parts.