IT STANDS! IT STANDS!
Finally, I carved the third hole out and fitted the leg. The one alone is a little longer than the other two, probably all the three will never be the same length but that's ok, I'm planning to use it in the garden where we don't have a square feet flat surface...
It's a little rickety for now, the two legs in the pair moves a bit, but not that much I could flatten the surface of the table with a chisel fine (now if I place a cube on it, it won't roll down). My plan to fix the little movement it has is to install "crossbeams", which will fix the legs in place relative to each other.
First I wanna debark the legs, then carve slots for the crossbeams on them, then make the crossbeams, then oil the whole thing, then put together, and finally drill holes in the legs at the crossbeams to fix it together with pegs.