By using less flour, you get a much more tender okonomiyaki. It's a
Chinese soup spoon, so it's about 2-4 tablespoons (depending on how
"heaping" you make it). If it seems to dry, add more yamaimo. If it
seems too wet, and a little bit more flour until you get the
consistency of an earlobe.

FWIW, that recipe of okonomiyaki makes the best okonomiyaki I've ever
had. Most places make the batter too thin, or don't use enough of
it. My friend's mother's recipe, in my opinion, is perfect!

You can also add tenkasu, finely sliced pink shoga, or finely sliced
konnyaku to the batter. The only one I would add, personally, is the
tenkasu (I hate that pink shoga stuff), but I never have any around.