Starting from the Fernwood trail head, go north on the Bonneville Shoreline trail. Do not turn left and go over the new bridge at 0.5 miles. Instead, keep right and go over an older bridge in about 0.2 miles. At 1.18 miles, the trail will split. Go right on the Great Western trail. The trail will switchback for a while, and then you will enter a thick forest. From the bottom of the mountain, you would never imagine a forest (with trees of this height) exists on the side of this mountain. It is certainly not visible from the valley floor.
At 5.21 miles there is a spring with some PVC pipe for collecting water (called "Cool Spring" on some maps). At 5.5 miles, you'll encounter ruins of an old campsite complete with an iron stove. It is very important you make a 90 degree left turn here at the campsite. The trail also continues to go straight (or slightly to your right), but you do NOT want to go there (the trail goes to the Kay's Creek Ridge Trail, and it is very faint in spots).
After you make that 90 degree left hand turn, you'll head over to some rocks with cairns, then up a very steep section. This loose rock steep section was named "Chinscraper" by the Wasatch 100 racers. [the course changed in 2016 so the race no longer traverses this ridge). Once you scramble up this steep section, you should see two large cairns -- 6 miles from your start at Fernwood. You have now intersected with the Kays Creek Ridge trail.
It is now 0.4 miles to the top of Layton peak. There is no real "trail", but it is easy to find your way to the top. Follow the obvious dirt patch heading higher in elevation. You will see another cairn marking where the Great Western trail heads south to Farmington. Stay to the left and make your way higher in elevation. The trail becomes more and more faint - just keep heading for the highest spot in elevation.