I always go to Peyto for Sunrise or Sunset so the light is directional but also go when theres some sunlight so you can get the brilliant colors of the lake. To get to this rock specifically, you have to walk up to the lake and on any trail you take you have to turn left once you get to a point where you can see the lake (ideally if you are heading to the wooden platform, go left from that). You have to walk for 10-15 minutes and you'll see the spot!