Coming from Bovec, drive towards Predil Pass/Trenta Valley. At the roundabout by the Hotel Mangart, take the exit for Predil Pass. Go straight until you reach Log pod Mangartom (10km / 10min).
Coming from Ljubljana, shortest route is via Kranjska Gora, Rateče, and then Italy. Make sure to turn left in Italy before you reach Tarvisio (the crossroads is well marked) to continue to the Predil Pass and then descend to the Koritnica Valley all the way down to Log pod Mangartom (120km / 1h 50mins).
Coming from Nova Gorica, the road will take you past Tolmin, Kobarid and Bovec (81km / 1h 30min).
Coming from Italy or Austria, you can reach Log pod Mangartom via Tarvisio going over the Predil Pass.