Parking just after the bridge at Plampinet. From there go through the village and pick up the GR5 heading east, follow it to the St-Rock Orat. To the left of the St-Rock Orat you see the start of the couloir, head up it and keep in it as it bends to the right. At the top of the couloir you can follow the ridge to the summit of Guion.
Ski back down the couloir till the St-Rock orat and the follow the GR 5 back to Plampinet. It is possible if there is snow down to the main road, to ski down straight from the 1715m point and miss out the zig zag GR 5 section.