Flanders mountain is the closest prominent mountain to become visible once you have reached Hyalite reservoir. It's the first in a series of peaks which form a ridge running all the way to hyalite peak. Although it's not particularly high in elevation when compared to the surrounding peaks, it offers fantastic views and a chance to get away from the more popular multiple use designated trails. The approach described here, will take you to a spectacular sub-alpine cirque lake surrounded by large volcanic cliffs. On some maps this lake is labeled Flanders Lake.
A rocky point called The Mummy can also be reached on this route. Some sort of weather equipment is stationed on this point.
This hike will require some bushwhacking and routefinding skills. There is no officially mapped trail yet one does exist and appears to be maintained from time to time probably by outfitters.
From Bozeman take south 19th to a right on Hyalite Canyon Rd. Take this gradually climbing winding road for about 10 miles to the dam and drive across it. At this point the road turns to dirt. At about 11.5 miles take a left at the sign for Emerald Lake and Palisade Falls. Bear right when you reach the Palisade Falls TH. After about .6 miles from Palisade falls TH you will pass a seemingly out of place talus field on the immediate left of the road. There are 2 turn offs to the right after this and the second is the best place to park.
Finding the trail: There is a network of old fire roads for the beginning of this canyon. The idea is to stay towards the creek. Eventually, the roads end and you cross over the creek to a somewhat maintained trail. This trail more or less follows the creek on the left side all the way to the gap guarding flanders lake. A good topo map of this canyon is key to finding your way and the proper point to turn off. A creek flowing out of flanders lake cascades down steep terraces. When viewing from the trail the best route up is on the left side. A trail may appear and disappear on the way up to the lake.
Unfortunately Beartooth Publishing's ever-popular Bozeman, Big Sky, West Yellowstone Outdoor Rec Map, does not provide enough detail for Flanders Lake to appear there. USGS Quadratic topos do however display the lake.