The route is marked from the main road above Bourg St Pierre, but it may be possible to drive slightly further up, to some parking above the village at Plan du Pey, 1827m, or even to the Alpage de Codanne. Follow the well-marked trail up the valley, above the Valsorey stream. You stay on the N side of the river, passing the hamlet of Cordonne, the Chalet d’en Bas and shortly afterwards taking the L fork, signposted to the Valsorey Hut.
The other path takes the route to the Velan Hut. Go past the Chalet d'Amont at 2197m, or stop for a break admiring the great views. Above here you continue SE with the help of ladders and chains to negotiate broken rocky terrain and a gulley, arriving at Grands Plans, 2502m. Now go NE more steeply on the rocky path to the prominent hut on the spur above.
This last section can feel like a relentless slog as you are starting to get pretty high, and the effects of the altitude will begin to be noticeable. You are rewarded with an amazing panorama from the hut, looking W to the Mt Blanc Massif, with all the major peaks clearly visible.