Manufacturing Microcontrollers for portable vaporizer by first prototyping with Arduino
Depends on how deep your pockets are. If you're willing to spend a lot then you can hire engineers and designers to create your product from scratch. You tell them to jump, and they'll ask "How high?".

On the other hand, spending some time with EDA and 3D modeling tools will save you a lot of money. You can then talk with your board service, assembler, and machinist as to how the pieces fit together and they'll deliver anything from bare PCBs and empty cases to a full, working product.

And then there's the homebrew route. You can go all the way to doing the reflow and machining yourself and not have to pay anyone else, but manufacture will be slow and the initial investment can be high.