1. Copy a build and place it alongside
The first two corners are the source box and the third is where the copy starts — keep the two boxes from overlapping
/clone ~ ~ ~ ~5 ~5 ~5 ~10 ~ ~ replace normal
What it does Will copy the region between coordinates ~ ~ ~ and ~5 ~5 ~5 and paste it with its first corner at ~10 ~ ~, copying every block including air, the source stays intact.