I've always mounted from the left... lean the bike towards me, and hook the right leg over the saddle.
I then clip the right foot in and get going, then the left foot clips in last. Unclipping, the left foot comes off and rests on the kerb / verge.
If it's flat pedals, it's the same order. But on flat pedals I seem to do the "hello cowboy" mount where the left foot starts "standing" on the pedal, and I do the skateboard skoot with the right leg on the left of the frame to get going, then the right leg gets thrown over the saddle when I have enough momentum.
I'm right handed if that matters, which to be fair, it does seem to have an influence!