I still "mantain" (i.e. "I haven't deleted") some pages from my long-defunct Traveller campaign, including guidelines on how to implement "complex research projects" in Traveller (lifted/stolen/adapted from Chaosium Ringworld).
(I also dabble in a similar cottage industry myself, as a Shodo student who sometimes sells or gives away his work, so I think I am qualified to answer ;) )
The guidelines use a generic task system based on T4 but with a modified 2D6 mechanic (you can find it under "YATTS" on the same page) and I believe that converting the research mechanics to a similar task/difficulty system should be pretty easy.
I suppose that any "produce something salable" could be modeled by composing tasks I label as "Theoretical Research", "Laboratory Research" and "Library Research". The actual production for the final object would probably work best as a Laboratory Research task.
You should decide, depending on what the PC is actually creating, if a failure means that the "artifact" is lost, or if it salvageable.
In the same spirit, an outstanding success could result in an object that can be sold at a higher price.
In general terms, you should define a flowchart with the steps to create a given "object", assign cost, times, and appropriate task roll to move forward to the next step, possibly including branches for critical success and failure – try to involve the player in designing the flowchart with you. (I've used Flowchart.com in the past.)
Here is an example "complex research project" flowchart to get your juices flowing (but try not to make things too complicated, or most of your session could be taken up by taking care of the cottage industry PC).