What are concrete examples for class G up to 14500?
It can be difficult to find these areas on a VFR sectional (there are very few of them anyway), but on an (FAA NACO) IFR en route chart they're shaded brown, so they stand out very clearly from the background. Here are a few grouped together in South Dakota.

IFR chart:



VFR chart:



At the western end of those areas there's a public airport, Bison Municipal (6V5):