St. Andrews Lake is a lovely high country lake along found along the 93-mile Wonderland Trail, but the lake can also be accessed via an out-and-back route starting from the Westside Road.
The hike begins with a long jaunt along the decommissioned section of the Westside Road, finally reaching the old St. Andrews Creek trailhead at around 8 miles in. After the junction, the St. Andrews Creek trail will switchback up out of a river valley and pop hikes out on a nice ridgeline before reaching Aurora Lake and the Wonderland Trail junction. Take a right on the Wonderland Trail to continue onward to your final destination of St. Andrews Lake and soak up the mountain views and wildflower meadows.