The best variety of Finger carrot seems to be "Amsterdam", which comes in various versions such as "Amsterdam 2", "Amsterdam 3" etc. I bought a pack of "Amsterdam 2 Solo" from Wilko, for the princely sum of 50p. A pack contains at least 200 seeds, which is more than enough for my needs.
On May 24th I sowed a generous number (maybe 25 - 30?) of the seeds in each of two tall pots filled with finely sieved soil with a bit of added compost. You definitely want to remove any stones. In the hot weather, they germinated in just a few days. [NB: keep the soil moist to improve germination rates.]
Now those pots are actually quite small in diameter so I will definitely be thinning out the carrot seedlings in order to leave maybe 12 or 15 in each pot.
The seeds hadn't all germinated when I took these photos. It's a good idea to wait until you judge that all those that are going to come up have come up, then you can remove the ones you don't want, leaving the others reasonably well-spaced.
During summertime carrots like these will take 2 - 3 months to develop fully. In the meantime I'll be making sure to water them frequently, but I'll stand the pots in saucers and water them from the bottom, so that the carrots put out long roots to search for the moisture.
With a bit of luck I'll end up with a small number of very special carrots, ideal for eating raw as a snack - maybe a pre-dinner Nibble like this!