I taught base-10 to my kids (pre school, ie 3/4) by teaching them the concept of number bases, and considering aliens with different numbers of fingers ... and

I taught base-10 to my kids (pre school, ie 3/4) by teaching them the concept of number bases, and considering aliens with different numbers of fingers ... and robots of course (my robots only speak binary!). Seemed to work somewhat. Mind you, despite having relatively good teaching in mainstream UK schooling they could all definitely have done/do with more headroom in their school maths.