Take them up and cross them. Place a hairpin so that it could tak hair from the upper braid and from the lower as well. I always put the pins from upwards down.
Wind the braids symmetrically and secure with hairpins. Short ones are handy.
Wind them once more to make them go up and secure with two hairpins. The braids should always lay flat on the head.
Then you can arrange the center cross so that the braids go under-over-under-over and keep this rythm when tucking the tails under or over the big loops. You may add a hairpin to the cross, but only after you have neatened the tails (to be sure all is (close to be) symmetrical).
Take two hairpins and secure the tails under the braids. I find the best to thread the tails first to the hairpins and then place them.
This was on my sister. Then I did it on myself. And what I saw at this photo??! Wrong.
And when I looked at the photo of my sister.. I messed the whole tutorial up:-DDD
Can you reveal when the mistake began? To compare, here you have the photo of my prototype, which is done correctly. And as a hint, it was inspired by a Celtic knot.
Although doesn't look like, this hairdo is quite ok to do on oneself. I rather use the mirror to make the French braids:-) Then you can feel everything by our hands, it's easy to get to know if it's symmetric or not.