At the Super Châtel gondola, take the stairs on the left and follow the lift for 40m up the slope (the only difficulty), then turn right and follow the balcony path towards the Lac de Vonnes.
The return is by the same path or by taking the shuttle bus.
Variant in the other direction from the Liaison Vonnes car park, cross the road by the footbridge or by bus at the Gabelou stop.