Internet searches are your friend. Searched for “flawless manmade diamonds and read the first five hits.
Apparently one can indeed make such gems in the garage, with a few million in equipment.
You had a Point?
You know what I mean. All diamonds have flaws but many can only be observed with an electron microscope. Diamonds that are made within the earth are formed at depth under high pressure and temperature. They take quite a while to form. I’ll let you decide how long. Because of the time required to make them, the carbon atoms can align in such a way that they appear to most analyses as flawless. At least the ones worth a pretty penny. My wife’s has a flaw that is visible with a hand lens because I didn’t want to pay a small fortune for a “flawless” one cuz I am cheap. Either way, you ain’t making one that can fool an expert in your garage. Unless you want to try cubic zirconium.