After the Skrulls briefly had the Illuminati, they were able to take several DNA samples from them. Dro'Ge proposed to King Dorrek VII that they conduct experiments with the samples and attempt to reverse engineer the DNA.
Years later after the destruction of the throneworld and when Queen Veranke was in power, he presented her with his results. Using their science and magics, they were able strip down the human, mutant, and Inhuman DNAs and create a new model of Super-Skrull warriors. Any sample that is obtained can be replicated. They have also found a way for their warriors to go undetected by all of Earth's magics and technology.