At the exit of Chapelle d'Abondance direction Chatel, take the road to les Ryz. Follow the road to the end (1595 m) at Sevan devant.
At Sevan devant, follow the little path which climbs through the meadows. You reach the farm of Braitaz (1762 m). Pass under the rock barrier of the Braitaz needle (1910 m) and reach the Outanne collar (1857 m) on the french-swiss border. Follow up the comb to Sevan collar (1891 m),. From here you have a nice view on the Arvouin lake.
On the right, in northern direction, walk over a grassy shoulder, and an easy rock step (1990 m) to the crest and the summit of Mount Lenla (summit cross)
No gear is necessary