A friend and I hiked up the slide last winter. Finding the slide was actually pretty straight forward. One could simply hike up the tributary that drains Marshall's southwest side. It can be accessed where it flows into Calamity Brook. In fact, the trail crosses this tributary. When we hiked it last year, we did not want to trespass so we continued on the trail to the property boundary and then backtracked along the boundary until we hit the tributary. This made the trip a little longer and brought us through a few areas of downed logs, but nothing too bad. With the new land purchase by the State of New York (or is it The Nature Conservancy) it may now be legal to head directly up the tributary from the trail.
The hike up the slide went very quickly. The hike from the top of the slide to the summit was a bear. The growth was very thick. We made sure the Herbery Brook route was broken out before we did the trip so we wouldn't have to descend down the slide. The slide does have avalanche potential, but my friend had a shovel, saw, etc. and was fairly well trained in assessing avalanche potential. He deemed it safe to travel on at the time, but you'll definitely want to stop and assess the situation.
John