Hike from Mnt Hostel near Gimmelwald to Rotstockhutte. Looking at AllTrails, there appear to be two main routes to Rotstockhutte. You either initially walk northwest (uphill) to connect with the east-to-west trail that goes from Murren to Rotstockhutte, or you initially walk southwest slightly downhill before the trail heads uphill and then northwest up to Rotstockhutte. (I haven't done this, so these are my guesses.) Look at all the linked AllTrails hikes that include Rotstockhutte to pick a route. Note that the more southern of the two routes has a gondola you can take up to Rotstockutte to skip the last third of the hike.