As somebody who has been watching the process for this for years, let me tell you that it is the exact opposite of easy, and nearly impossible.
And it's nearly impossible because current wealth holders are able to stop it from being built. And in most areas where there are housing shortages, locals and local governments consider the current land "built out" meaning that the zoning does not permit more housing or more height than is already built, an the notion of changing these arbitrary restrictions is so inconceivable that it almost never happens.
This is what has really changed over the past yes decades to make housing prices soar: refusal to allow more housing to be built on existing land.