So I guess there is no way to aggregate a black hole. It has to be the result of some almost instantaneous phenomenon such as the rapid collapse of a star.
I think stellar collapse of some sort would be the only practical way, or we could snag six neutron stars and collide them.
If we could confine our accelerator-made hole to a very fine degree, maybe we could feed it more protons until it grew. But the accelerator-made hole will be very, very small with respect to a nucleus and it will have a charge, making this difficult.
I’ve read theories in which most large masses already have micro or mini holes. They evaporate at a high rate and this is balanced by the rare interactions with baryonic matter (there is a huge space between nuclei in normal matter, making collisions rare).
Making accelerator holes that are at relativistic speed, if it’s possible, may mean that we could take a mass like the Moon, and zap so many microholes at it that we’d condense or collapse it, then we can feed it chunks of rock to grow it. Relativistic velocity will make it last longer as seen in our reference frame, like accelerating neutrons extends their 11s half-life. Making a hole by collision leaves a hole with low residual velocity.
These concepts, though, are well beyond our current capabilities. They make fun for science fiction writers, though!
Frederick Pohl’s Annals of the Heechee is a good example, and short stories like “The Hole Man” are good.