Nether Based Designs
Nether based gold farms use normal mob spawning mechanics to spawn zombified-pigmen on magma block platforms and then bring them to a central area where they can be killed. These are the recommended type of gold farm on Vanilla+.
Above are two slight variations of a nether based gold farm. The one on the right is a faster, but more complex and expensive to build. For both of these types of designs there are some important things to remember specifically for Vanilla+.
Overworld Based Designs
Overworld based gold farms utilize a mechanic where pigmen spawn inside of nether portals. They involve a bunch of massive nether portals, which makes them quite expensive to build.