Park at Col de Marocaz.
(S/E) Take the wide path that climbs south-west. When you reach a hairpin bend, stay on the path. Pass the Croix de Fer and continue south to reach a large crossroads.
(1) Take the path on the left to go around Rochefort to the south, following the path. You will reach another crossroads before the Col du Mont.
(2) Take the marked path on the left and continue to Col du Mont. Once at the pass, turn right and head southwest. Continue to Rocher de Manettaz and enjoy the view, 30 metres south of the summit.
(3) Continue along the ridge to quickly reach Col du Mollard.
(4) Continue along the ridge heading west to climb up to Roche du Guet.
(5) Continue along the route to the crossroads after Col du Mont. Turn left and then quickly right. At the next fork, continue to the right and descend into the woods towards La Thuile.
(6) At the crossroads near the first houses of the hamlet of Lac, climb up to the right towards Col de Marocaz. Return to the initial crossroads, which marks the start of the circular route.
(1) Take the path you came on to return to the Col de Marocaz car park (S/E).

unglasses
Starting at point 1, there is a rather uninteresting forest road for about three or four kilometres, after which the hike begins on good paths with beautiful views of the valley and the surrounding mountains. I did not find the alternative route that starts at point five to reach the lake; in my opinion, it must be quite a long way.