When we think of 3D culture, its always a spheroids which resembles cancer stem cells properties and phenotype. In in-vitro condition, its "enrichment of CSC" process means we enrich monolayer cell line to become 3D spheroids, gain of stemness feature for further study.
Now, how each cell line respond to enrichment condition and forms robust spheres is depends itself on cells line.
so you can start with most preferred cell lines : H357, SCC4, SAS, JHU, OECM-1 and CAL 27.
There are different methods of making 3D cultures (usually tumor spheroids). Some cell lines do not form spheroids by one method, but it is possible to make them by applying another one. Sometimes you need just simply to add fibroblasts, they help a lot. You may find many methods described in this publication:
https://www.nature.com/articles/srep19103
Personally, I prefer 3D Bioprinting method which helps a lot to make spheroids even if other methods do not work (from my own experience).