After the cell reaches 4.2 V in the "CC" part of the cycle it is "mostly" charged at that point (maybe 2/3rds full, maybe more). So in a sense the CV part of the charge is a kind of "topping off" of the cell.
There is no real advantage in charging lithium ion cells too slowly. As long as you don't exceed the manufacturer's recommended maximum charge current the CC value you choose doesn't really matter.
However, do take note of the warnings from others here. If a cell is of poor quality, or damaged, or if you exceed its charging parameters, it could burst into flames in a very spectacular way. Always charge in a fire safe location, on concrete, under constant observation, where erupting flames can do no damage. You can buy fireproof "charging sacks" to put the cell in while charging, which will contain any unexpected conflagration. It is no exaggeration to say that people have burned their house down while charging lithium cells.