How do you concrete it with the mesongun?

“One thing puzzles me, Mr. Biebursson—and I am a technical
man myself—the use of congealed water, this vitreous quartzlike
substance. How do you form the water into these patterns, these
compound curves, and hold it so while you concrete it with the
mesongun?”

 Biebursson smiled. “No problem, with the natural advantages that are
mine. I am a spaceman—I work where the forces of gravity have no
effect, where the whole of time is mine for
contemplation.”

Jack Vance, To Live Forever