they are leveraging the givens, lots of solar energy and pulverised rock heated to 1300°c in a vacume will sinter into bricks. I think that a more advanced version would also yield oxygen in significant amounts and other volitiles that could be captured. The moons surface composition is well understood, and in any case,1300°C will sinter almost any random rock debrit into a brick, the harder part will be mortar, or perhaps making something with mechanical joints, like stone henge, or lego. Pyramids on dark side of the moon Of course any moon base will be located next to one of the permanently shaded craters where water ice , hopefully other ice, can be found for making fuel and other uses.