Applying a rocky edge to upper level of layout

Here I have been challenged to apply a rock finish to the edge of the upper portion of the layout. We could not use rock castings on the extreme edges because the walkway is narrow and plaster could damage a locomotive being carried by a user. Instead, I used fiber decor and foam. I did however use rock castings on the inner edge along the soon to be river bank. I sandwiched foam sheet around the plywood to give it thickness and strength, filled in the seams with expanding foam in a can and later carved the excess off. Then I applied the fiber decor and made rock impressions with a putty blade.