They learn from first principles by starting to organize things. The tools used for working from first (principles, materials, observed rules etc.) are based on

They learn from first principles by starting to organize things. The tools used for working from first (principles, materials, observed rules etc.) are based on organizations of observations of whatever is at hand. If you're learning from someone else's first principles and it's not working for you, which is really common, try the break-fix opportunistic approach instead. Take something already built for purpose and use it until it breaks, then fix it. Always use every workaround possible in the meantime. Work around whatever you can't fix; even if you think you'll end up with a pile of workarounds, it will be a really well understood pile which is quite different. This way you'll still get to first principles eventually as you understand the system more. You'll have infinite chances to design your own as your knowledge and experience increase. But some people have better results working in this way instead of starting from first principles. They are sometimes known as results-oriented personalities as opposed to process-oriented. In that they work backward from the needed result (which may be even completely improvised) as opposed by working forward with their own organizational ground-up process.