As Dale has pointed out there's plenty of information on Google about this process, that is also known as as investment casting in certain circumstances.
Wikipedia has a good explanation with some diagrams.
Investment cast lugs are still readily available even though, by and large, lugged steel frames are no longer popular with the larger frame manufacturers. There are some signs of a come-back though as the market rebounds after the excesses of carbon.
Lost wax lugs are great BUT..they are not malleable and cannot, without too much effort and skill, be adjusted from the angle at which they are cast..therefore they can restrict the frame-builder's freedom of action and design. But they're OK if all your frames are like peas out of a pod.
Norris Lockley...feeling argumentative tonight..blaming it on the incessant rain..Settle UK