Stir, strain, old fashioned with one large ice cube, no garnish.
I unfortunately don't have Amer Picon but I used Torani Amer, which is what I recommend here. I believe this is a great introduction cocktail to single malt scotch. The honey and herbs pair well with the smooth sherry tones and finish with Macallan and the bitter sweet orange of Amer. Cynar provides the earthy bitter to round out the finish.
The name is a play on the Rusty Nail, from which the inspiration for this cocktail was birthed.