It is easy to overwater a tiny tuber in even a 4" pot before it gets growing. I don't see roots on the tubers in the picture, so it will be hard for them to take in water until they grow some. I would start by potting them up in soil that is moist but not wet (the classic moderately-wrung-out-sponge), with the entire tuber covered, and then not water until a sprout showed above the soil. If the sprout comes up weak and skinny, that is my sign that I should just leave it to grow, and probably it will end up as a pot root. If it looks strong, even if it is on the small side, it may be okay to take a cutting. I start my really tiny tubers in 2-1/2" pots, like fuchsia starts come in. I have taken cuttings from some of them.
