I don't know about you but I hate test tiles. I only need about a half-dozen tests at a time, so I'd much rather use small, quickly-thrown tea bowls (or wine cups, as they are known at my house), which at least have the potential to become beautiful objects. They also have to potential to become hideous or just blah, which is why they are called "tests," so I don't want to invest a bunch of time in them; specifically I don't want to have trim them. I found a trick to make that easier.
Throwing off the hump is the best way to make small things fast but has the disadvantage of creating a very uneven bottom when you use the cut-off wire. Mine always looked like this:
The pots always needed trimming, if they were to sit flat. To streamline the process in the case of test pieces, I now cut them off with a piece of thread. Once forming is done, I use the point of a rib to create a little notch at the very bottom of the pot. I place a piece of thread (a bright color is easier to see) in that groove, wrap it around, and then cross the ends on the near side and pull in opposite directions.
The result is an even bottom which only needs a quick swipe with a rib to finish it nicely.